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UP
DOWN
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LEFT
TM
CP9110
Table of Contents
Vehicle Service Information ............. 2
Safety Precautions ............................ 3
Section 3:
Help and Troubleshooting
Tips ....................................19
3-1 Tool Problems ............................. 19
Section 1:
Welcome to The Scan Tool ..
4
3-2 Car Problems .............................. 20
1-1 Features ........................................ 4
1-2 The scan tool ................................. 5
1-3 What You Get ................................ 6
1-4 Cartridge and Installation .............. 6
1-5 Cables and Adapters..................... 7
3-3 Scan Tool Self-Tests ................... 20
• Display Test ........................... 21
• Keyboard Test ........................ 21
• Memory Test .......................... 21
Section 4:
How to Order
Accessories ......................22
4-1 Where to Buy?............................. 22
4-2 Call Actron Direct ........................ 23
4-3 E-Mail & Internet address ........... 23
1-6 Operating the scan tool ................. 9
• Powering-up the scan tool ....... 9
• Keyboard .................................. 9
• Display.................................... 10
• Lists, Menus, & Questions ..... 10
• Other Functions & Keys ......... 11
1-7 Scan Tool Setup .......................... 12
FULL ONE (1) YEAR WARRANTY
ActronManufacturingCompany, 15825Industrial
Parkway, Cleveland, Ohio 44135, warrants to the
user that this unit will be free from defects in
materials and workmanship for a period of two (2)
years from the date of original purchase.
Section 5:
Appendix ...........................24
Section 2:
Computer Vehicle Basics.. 13
Glossary of Terms ............................. 24
15825IndustrialParkway
Cleveland,Ohio44135
U.S.A.
Anyunitthatfailswithinthisperiodwillberepaired
or replaced at Actron’s option and without charge
whenreturnedtotheFactory. Actronrequeststhat
a copy of the original, dated sales receipt be
returned with the unit to determine if the warranty
period is still in effect.
2-1 Basics of Computer-
Controlled Cars ........................ 13
2-2 About Codes................................ 16
2-3 When to Read Codes .................. 17
Toll free U.S.: (800)228-7667
This warranty does not apply to damages caused
by accident, alterations, or improper or unreason-
able use.
ACTRON MANUFACTURING COMPANY DIS-
CLAIMS ANY LIABILITY FOR INCIDENTAL OR
CONSEQUENTIALDAMAGESFORBREACHOF
ANYWRITTENWARRANTYONTHEUNIT.
©2004ActronManufacturingCo.
AllRightsReserved.
0002-002-2186
1
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1-2 The Scan Tool
Section 1: Welcome to the Scan Tool – Basics
Actron’s scan tool was developed by ex-
perts in the automotive service industry to
help you diagnose today’s vehicles and
assist you in trouble-shooting procedures.
Computer-controlled vehicles have a net-
work of sensors that creates a series of
inputs to the engine computer. The com-
puter interprets these inputs and sends
outputs (commands) back to the network
to control air, fuel, vacuum, spark and
other critical functions. When a problem
occurs, the computer will store a record of
the event, and take corrective action to
adjust the circuit at fault. If the circuit does
not respond, or the problem cannot be
corrected, a trouble code is stored in the
computer’s memory. In some cases, the
Check Engine light may also be activated.
The scan tool will allow you to monitor
these vehicle events for trouble-shooting
and diagnosis, and to read codes from
the computer’s memory to pinpoint prob-
lem areas.
Lookup feature allows you to reference
code descriptions without having to page
through an instruction manual.
1-1 Actron Scan Tool Features
The Actron scan tool has
many features that you
would expect in scan tools
used by the professionals:
When the scan tool is connected to the
data connector, a communication link is
established, allowing the scan tool and
the vehicle’s on-board computer to ex-
change information. The way in which this
information is exchanged is referred to as
a data stream.
TM
• Large 4 line x 20
character LCD display
• High-impact plastic case
• Durable, easy to use
keyboard
• Removable vehicle cable
adapter
®
®
by
As you use the scan tool, you will become
more proficient in trouble-shooting ve-
hicles using the detailed help messages
and code description information. Actron
will also help you become skilled in using
the scan tool for more than just “scanning”
the vehicle data list. We will show you
many other uses that will expand your
diagnostic limits by using the information
contained in the application manuals that
come with your Application Cartridge. No-
start, driveability, and emission problems
will be easier to diagnose than ever be-
fore.
P
U
N
W
O
D
T
H
IG
R
T
F
LE
• Removable power cable
Scan Tool & Application Cartridge
Vehicle Manufacturer Application Cartridges
The manufacturer-specific Application Cartridges offer a universal approach in chang-
ing software as vehicle technology changes. Actron’s separate cartridge and cable
system lets you add vehicle applications to meet your needs.
The scan tool uses state-of-the-art 16 “bit”
microprocessor technology and has twice
the computing power of some scan tools
costing thousands of dollars! The scan
tool is programmed to interpret the com-
puter signals and provide you with a “real
time” readout of vehicle data. More impor-
tantly, the software programs are written
to provide you with detailed, full-screen
readouts of all data. In addition, the Code
Cartridge Systems:
GM Cartridge
Ford Cartridge
Chrysler Cartridge
OBD II
1984-1995
1984-1995
1989-1995
1996-up
198
4-1
GM
9
95
995
ER
9-1
S
198
CHR
L
Y
Optional Cable Adapters:
Chrysler CCD / LH – 6 Pin
Ford/Mazda MECS – 6 Pin
GM J1962-OBD-II – 16 Pin
Ford J1962-OBD-II – 16 Pin
Chrysler J1962-OBD-II – 16 Pin
Professional-Style Adapter Cables:
GM ALDL — 12 Pin
Ford EEC-IV/MCU — 7 Pin
Chrysler SCI — 6 Pin
4
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tridge into the cartridge opening. Align the
cartridge slots with the “keyway” on the
main tool bottom opening. Continue to
gently push the cartridge into the opening
until you feel the main “edge connector”
resistance, then push to engage the car-
tridge to the cartridge stop. The cartridge
is engaged when the alignment of the
serial number tag is even with the top
edge of the Main Tool opening edge and
flush against the cartridge stop. Refer to
the example.
To remove the Application Cartridge simply
grasp the cartridge end and pull away from
the main tool. This action will disengage
the cartridge from the edge connector. Con-
tinue to pull the cartridge out of the open-
ing the rest of the way.
1-3 Actron CP9110 – What You Get
When you receive your scan tool, take time
MODEL NO.
SERIAL NO.
ACTRON MFG.
© COPYRIGHT 1995
PATENT PENDING
to review all package contents.
CP9110
123456789
The Application Cartridge serial tag is
locatedonthetopcenterofthecartridge. This
serial tag will always be visible when the
cartridge is inserted in the main tool.
Actron Manufacturing warrants the software programs to
be accurate to the level of information released by the
Vehicle manufacturer at the time of release.
NOTE: You should always have the Ap-
plicationCartridgeinstalledbeforeyou
connect your unit to the power supply.
NEVER UNPLUG THE CARTRIDGE
WHEN POWER IS APPLIED!
(800) 228-7667
1-2325
Main Tool Model and Serial Tag
Please take time to review all important
documents enclosed. Be sure to review
both boxes for contents.
Review Box Contents
Main Tool Box
©
COPYRIGHT 1995
PATENT PENDING
CP9111
123456789
1984-1995 GM
In addition to the scan tool you should
have received the following items in the
main tool box:
• The Scan Tool
• Carrying Pouch
Cartridge Model and Serial Tag
1-5 Power Cables and Vehicle Adapters
Thescantoolcomeswithamainpowercable
designed to plug into the vehicle cigarette
lighter.Theotherendofthecableplugsintothe
scantoolasshownbelow.
Your scan tool has been designed to
operate at the same voltage levels as your
vehicle’s computer. It requires a minimum
of 8 volts to power-up. The scan tool is
circuit protected from voltage variations
and power surges. Should you have a
problem with power-up, review Section
3-1: Tool Problems to verify the nature of
yourproblem.NOTE:Somevehiclesshutoff
powertothecigarettelighterreceptaclewhen
theignitionkeyisintheOFForSTARTposi-
tions.Checkyourvehicletodeterminewhether
this is the case.
• Power Cable
• Main Tool Operator's manual
Before You Start
Take time to review the proper procedure
for powering-up your scan tool. The fol-
lowing section, Cartridge and Installation,
should be read before proceeding! This
will help you become familiar with all
operating procedures.
Application Cartridge Box
The Application Cartridge box that you pur-
chasedshouldcontainthefollowingitems:
• The Application Cartridge
• Vehicle Cable Adapter
• Application Manual for that vehicle
Connecting to Vehicle
Cigarette Lighter
E
L
F
T
R
G
I
H
1-4 Cartridge and Installation
T
D
O
W
N
Optional
Battery
Clip
y
b
U
P
®
®
Review the Application Cartridge instal-
lation procedure before you power-up
your scan tool. Hold the cartridge, serial
number tag up, and slowly insert the car-
M
T
TM
®
TM
®
by
®
®
by
Connecting to Scan Tool
UP
UP
DOWN
RIGHT
LEFT
DOWN
RIGHT
LEFT
Occasionally, you may find it necessary to
connect directly to the vehicle’s battery. In
these cases you may obtain an optional
battery clip adapter from Actron. Actron
also offers an AC power adapter to power
the scan tool with standard 110V wall
power. Both of these accessories may be
purchased directly from Actron.
TM
MODEL NO.
SERIAL NO.
ACTRON MFG.
©
COPYRIGHT 1995
T PENDING
1995
GM
®
®
by
UP
DOWN
RIGHT
MODEL NO.
SERIAL NO.
ACTRON MFG.
COPYRIGHT 1995
PATENT PENDING
©
LEFT
AC 110V to 12V
Power Adapter
CP9110
12345678
1984-1995
GM
1984-1995 GM
Application Cartridge Installed
7
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Vehicle Cable Adapters
1-6 Operating the Scan Tool
Your scan tool Vehicle Ap-
plication Cartridge pack
Keyboard
Powering-up the scan tool
will contain the Applica-
tion Cartridge, application
manual and vehicle cable
adapter for one manufac-
turer (GM, Ford, or
Chrysler). The vehicle
cable adapter will be in-
stalled on the scan tool by
locating the large connec-
tor receptacle on the top
right side of the main tool.
Insertthevehiclecableinto
the scan tool receptacle and use the two
“thumb screws” to secure it to the connec-
tor as shown in the illustration below. Note
that you will feel a firm seating of the cable
as you secure it to the scan tool connector.
The vehicle cable adapter should always
be connected to the vehicle before power
is applied to the scan tool. This will enable
the scan tool to maintain a proper ground
between itself and the vehicle. If you have
connected to the vehicle, powered-up the
tool, and have difficulty establishing a link
between the scan tool and the vehicle,
check the following:
The scan tool software was designed for a
“userfriendly”approachinnavigatingthrough
operationalmenus.Thismakesthescantool
easytooperate.Simplyfollowtheinstructions
thatmatchthekeyboardsymbolsandyouwill
beusingyourscantoollikeanexpertinnotime.
Sincethekeyboardissealed,adampclothcan
be used to gently clean the surface. (Cau-
tion: DO NOT USE SOLVENTS LIKE
ALCOHOL! This could remove the
keyboard paint!)
The scan tool can be powered-up in three
ways. The most widely used way is with
the supplied cigarette lighter adapter. The
scan tool can also be powered up by using
the optional Battery Clip Adapter or 110/12V
AC Power Adapter. If you are powering-
up the scan tool for vehicle testing, then
make sure you connect the appropriate
cable to the data connector before you
supply power to the scan tool. If you do not
connect the vehicle data cable now, the
scantoolwillletyouknowthatyouhavenot
connected the data cable. If you just want
to power-up the scan tool to do self-tests,
then you do not need to attach the cable
to the data connector.
Connecting the
Vehicle Adapter Cable
When attaching the data cable to the ve-
hicle, take time to review the specific ap-
plication manual for the cartridge you are
using. This will instruct you on correctly
connecting the cable to the vehicle. Many
of the vehicle adapters are “keyed” so that
the adapter will fit only one way. If you find
that you have a special vehicle situation or
the adapter does not fit, call 1-800-
ACTRON-7forassistance. Alwaysdouble
check the application section to be sure
that you are following the proper hook-up
directions. Forfurtherhelpthatisnotavail-
able in the scan tool help screens, see
Section 3: Actron Help for solutions to
your scan tool problems.
Scan Tool Keyboard and Display
UP
DOWN
RIGHT
LEFT
When the scan tool powers-up, a series of
screens is displayed. The screens start
with a “Welcome” screen and end with a
“Key Button Help” screen.
WelcomeTo
TheScanTool
ByActron
Keyboard Functions
The scan tool uses 8 keys to navigate
through the software-user interface:
PressHELPForKey
ButtonInformation.
1. Is the ignition on?
As you review the CP9110 Features sec-
tion on page 1-1 and 1-2, you will note
there is a complete view of accessory
vehicle adapter cables. They are for spe-
cial applications that only apply to certain
vehicles. If your vehicle is one of these,
you can order cables direct from Actron
by calling (800) 228-7667.
ENTER
Used to enter or answer a
2. Verify you have connected the vehicle
data cable to the vehicle’s Data Link
Connector (DLC).
software request.
PressENTERToCont
HELP
Used to request help when
the symbol is in the upper right hand
corner of the display.
3. Confirm that proper vehicle information
was entered into scan tool.
Welcome & Key Button Help Screens
The screens in between the “Welcome”
and the “Key Button Help” screen are for
a tool self-test and the cartridge software
version. Refer to this software version if
you need to contact Actron’s technical
support line with a problem. If you wish to
review the key button definitions, then
push the HELP key; otherwise, press
ENTER to continue forward.
FUNCTION Used to return user to
manufacturer’s function list.
BACKUP Used to move one screen
back in scan tool flow.
ARROWS UP or DOWN are always
used to move the solid cursor in the
direction of the arrow or scroll the data
list in the direction you want to move the
list
LEFT orRIGHTarrowsmove
the cursor in the direction of the arrow
and allow you to customize a vehicle
data parameter list.
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Display
(NOTE: This is a GM Function List –
Function Lists for other manufacturers
may differ slightly.):
In these screens, brackets will automati-
cally be next to the default response. If you
wish to accept the default choice, simply
press ENTER. If you wish to change the
answer, use the LEFT or RIGHT arrow key
to move the brackets next to the other
response and press ENTER.
GMFunctionList
7)BeeperOn-Off
8)English-Metric
9)CodeLookup
The scan tool has a 4 line x 20 character
liquid crystal display (LCD) for easy view-
ing.Thismakesthescantool“userfriendly”
by offering a large viewing area to display
most Help and Instructional messages.
This also puts more information on the
display instead of referring you to printed
materials. Again the display will support a
number of helpful characters that will
prompt you through test routines. These
characters are shown below:
GMFunctionList
1)ReadCodes
2)Erase Codes
3)View Data
Notice now that there is only an arrow
pointing up in the last column. This indi-
catesthatyouhavereachedtheendofthis
list, and that all other choices are on
previous screens. You can return to those
screens by pressing the UP arrow key.
(NOTE: This is a GM Function List – Func-
tion Lists for other manufacturers may
differ slightly.).
Other Functions & Keys
Note how the cursor is pointing at 1) Read
Codes. If you wish to read trouble codes,
press ENTER to select that function. To
make a different choice, such as viewing
data, use the DOWN arrow key to move
the cursor down next to 3) View Data and
press ENTER. This will select the View
Data function.
As you have reviewed moving through
lists and functions in earlier sections, you
probably noticed several other symbols
on the screen. In the upper right-hand
Question Mark in upper right corner
means there is help available for this
screen.
corner of some screens, there is a large
.
These up and down arrow characters on
the screen are used throughout the scan
tool’s software. The UP and Down arrow
keys work exactly the same way, even if
you are just scrolling through text such as
the On-Line Help screen shown below:
This question mark indicates that On-Line
Help is available for that particular screen:
Bell in lower right corner means the
sound alert is on or active.
OperatingError.
CheckConnections!
TryAgain?
Sometimes, a list will be longer than three
or four items, and will not fit on a single
screen. In these cases, the down arrow
symbol ( ) is visible in the last column of
the display, indicating that there are more
choices on the next screen:
Cursor used to select menu choice.
Down Arrow indicates there is addi-
tional information on the next screen.
<Yes> No
3.TESTCONNECTOR:
DAMAGED/LOOSEPINS?
4.TOOLSETUPOK?
CORRECTVINS,ETC?
Up Arrow indicates there is additional
information on previous screen(s).
To enter On-Line Help, press the HELP
key. For the screen above, the help mes-
sage would look like this:
GMFunctionList
1)ReadCodes
2)Erase Codes
3)View Data
Below is a screen showing how these
symbols will look on your display (NOTE:
This is a GM Function List – Function Lists
forothermanufacturersmaydifferslightly.):
RECHECKFOLLOWING:
1.IGNITIONKEYON?
Note that there are no choices to make
here, and that there is no cursor to move.
There are, however, up and down arrows
in the last column. These arrows indicate
that there are other screens before and
after this one. Using the UP and DOWN
arrow keys, you can scroll through the
entire message.
2.HOOKUPTOVEHICLE
TESTCONNECTOROK?
GMFunctionList
4)Record Data
5)PlaybackData
6)Field Service
To go to the next choice, use the DOWN
arrow key to move the cursor down the list.
NOTE: Pressing the DOWN arrow key
moves the function list one line at a time.
After several DOWN arrow key presses,
the screen below appears.
All On-Line Help screens have their text
typed in ALL CAPITAL LETTERS. This is
another reminder that you are viewing On-
Line Help screens and not screens asso-
ciated with a function of the Function List.
Some On-Line Help messages are longer
than one screen. If this is the case, the
Occasionally, you may be asked a ques-
tion by the scan tool which requires a
response. These will always be YES or
NO questions, and are answered in al-
most the same way you make choices on
a Function List. Below is an example of a
YES/NO question:
Lists, Menus, and Questions
GMFunctionList
4)Record Data
5)PlaybackData
6) Field Service
The scan tool is designed to be as intuitive
as possible. That is, its functions and con-
trols should be easy to understand and
use the first time you try it. All scan tool
menus and screen lists operate the same
way. By using the UP and DOWN arrow
keys, you can move the cursor to a menu
selection of your choice. The ENTER key
selects that function. Below is an example
of a Function List with several choices
arrow symbols (
) will appear in the last
column of the display. A means there is
more On-Line Help information available
on the next screen. A
means there is
Now notice that there are arrows pointing
up and pointing down in the last column.
This indicates that you can use the UP
arrow key to move the cursor to the previ-
ous screen or press the DOWN arrow key
several times to move the cursor to the
third screen, shown below:
ViewInstructions
ForCreatingCustom
DataList?
more On-Line Help information available
on the previous screen. Use the UP and
DOWN arrow keys to page up or down
through a series of On-Line Help screens.
Yes <No>
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The On-Line Help screen shown above
hasa inthelastcolumn. Toviewthenext
On-Line Help screen, press the DOWN
arrow key. That screen is shown below:
1-7: ScanTool Setup
Section 2: Vehicle Computer Basics
Tool Setup is used to change the scan
tool’s default sound and measurement
unit settings. To change the scan tool’s
default settings, select the Tool Setup
option from the Function List (NOTE: This
is a GM Function List – Function Lists for
other manufacturers may differ slightly.):
2-1 Basics of Computer-Controlled Cars
3.TESTCONNECTOR:
DAMAGED/LOOSEPINS?
4.TOOLSETUPOK?
This section explains the engine com-
puter control system, the types of sensors
and how the computer controls engine
fuel delivery, idle speed and timing. Addi-
tional information may be found in techni-
cal support books at your local library or
autopartsstore.Themoreyouknowabout
the computer system, the better you can
diagnose vehicle computer problems.
gine. It is still an internal combustion en-
gine with pistons, spark plugs, valves, and
camshaft(s). The ignition, charging, start-
ing, and exhaust systems are very similar
as well. You test and repair these systems
just as before. The technical manuals for
these components show you how to per-
form the tests. Additionally, compression
gauges, vacuum pumps, dwell/tach
meters, engine analyzers, and timing
lights will continue to be used.
CORRECTVINS,ETC?
GMFunctionList
7)BeeperOn-Off
8)English-Metric
9)CodeLookup
Notice now that both arrow symbols (
)
are visible in the last column of the display.
This indicates that you can either page up
to a previous On-Line Help screen, or
page down to the next On-Line Help
screen by using the UP and DOWN arrow
keys. The previous On-Line Help screen
is always the one you just viewed, just as
with Function Lists.
After selecting the Tool Setup option, you
are given the choice to change either the
ScanTool’smeasurementunitsorwhether
Computer controls were originally in-
stalled on vehicles to meet federal gov-
ernment regulations for lower emissions
levels and improved fuel economy. This
began in the early 1980’s when basic
mechanical systems were no longer able
to accurately control key engine param-
eters. A computer could be programmed
to control the engine under various oper-
ating conditions, making the engine more
reliable. While these early systems were
very limited in the scope of their control,
providing only 10-14 trouble codes, they
did help guide the vehicle repair process.
the beeper will be On or Off. If the bell (
)
The Engine Computer Control system
symbol appears in the lower right hand
corner of the display, then the beeper is
turned On.
Another symbol on the screen you might
have noticed is the bell ( ) symbol in the
lower right-hand corner as shown below:
The vehicle’s on-board computer, or
Powertrain Control Module (PCM), is the
“heart” of the system. It is sealed in a metal
box and connected to the rest of the en-
gine by a main wiring harness. The PCM
is located, in most cases, in the passenger
compartment, behind the dashboard or in
the “kick panel” position, although some
manufacturers locate the computer con-
trol module in the engine compartment
area. Most PCMs can withstand a lot of
vibration and are built to live in a rugged
environment.
SetupToolFor
PressHELPForKey
ButtonInformation.
1)English/Metric
2)BeeperOn/Off
PressENTERToCont
Depending on whether you select English/
Metric or Beeper On/Off, the ScanTool will
display one of the following screens:
This bell symbol indicates that the sound
alert is on or active. Each time you press
akey,youshouldhearabeep.Ifyoudonot
see this symbol, then the keys should
remain silent when pressed. Information
on changing this setting is found in section
1-7: Scan Tool Setup.
Today, computercontrolshavemadecars
and trucks faster, cleaner, and more effi-
cient than ever before. In fact, without the
government mandates for fuel efficiency
and emissions control, cars and trucks
today would not be nearly as powerful,
reliable, and comfortable as they are.
MeasurementUnits
English(Default)
Metric
The PCM is permanently programmed by
the factory engineers. The program is a
complex list of look-up tables and instruc-
tions telling the computer how to control
the engine based on various driving con-
ditions. To do its job, the computer uses
sensors to know what is happening and
then provide instructions back to a net-
work of switches and actuators through-
out the vehicle.
BeeperSound
On(Default)
Off
What the computer controls:
The main control areas of the vehicle
computer are fuel delivery, idle speed,
spark advance, and emissions controls.
Some on-board computers may also con-
trol the transmission, brakes, and suspen-
sion systems as well.
When the beeper sound is turned Off, the
bell ( ) symbol will no longer appear on
the lower right hand corner of the display.
Sensors, switches, and actuators give
the computer information
NOTE: If you change the Beeper and
Measurement Units to a setting other than
the default, then all changes will revert
back to the default settings the next time
the scan tool is used.
What has not changed?
Sensors are devices which measure op-
erating conditions and translate them into
signals the computer can understand.
A computer-controlled engine is very simi-
lar to the older, non-computerized en-
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sary—to give the O2 sensors time to warm
up to operating temperature.
Some examples of sensors: thermistors
(for temperature readings), potentiom-
eters (like a throttle position sensor), re-
lays (for voltage and signal readings), and
signal generators (such as an 02 sensor).
How the computer controls fuel deliv-
ery
position, manifold pressure (vacuum),
air flow and RPM.
As long as the engine and O2 and Coolant
TemperatureSensorsareatoperatingtem-
perature, the computer can operate in the
closed loop mode. Closed loop mode in-
sures that the air/fuel mixture is at the ideal
14.7:1 air/fuel ratio needed for efficient
combustion. But in stop and go cycles, the
O2 sensor may in fact cool down enough
that the computer will need to rely on a set
of internal parameters and go into open
loop mode again. In some cases, this may
also happen during extended periods of
idling. Many newer vehicles now use
heated O2 (HO2S) sensors to prevent this
condition.
Engine operation and emissions perfor-
mance depend upon precise fuel delivery
and ignition control. Early computer sys-
tems controlled fuel by electronically ad-
justing the carburetor metering and jet
systems. Soon, however, this was re-
placed by the more precise fuel delivery of
fuel injection.
• Air intake. Sensors used are: mass air
flow, manifold absolute pressure, mani-
fold air temperature and RPM.
The network of sensors has the job of
deliveringinformationthecomputerneeds
to know by converting it into electrical
signalsthecomputercanunderstand. Sig-
nals running from sensors to the PCM are
referred to as “inputs.”
• Air/fuel mixture status. Sensors used
are: oxygen sensor(s).
NOTE: Not all engines use every sensor
listed above.
In an electronically carbureted system,
the computer simply controls fuel flow
based on how far the throttle is opened by
the driver. The computer “knows” how
much air can flow through the carburetor
at various throttle openings, and adds the
appropriate amount of fuel to the mixture
at the carburetor.
Sensors monitor key things such as:
• Engine Temperature
Open and Closed Loop Modes:
Open or closed loop operation refers to
the way the computer is deciding how
much fuel to add to the air entering the
engine. During cold start and other low
demand, low temperature situations, the
computer operates in open loop mode.
This means that it is relying on a set of
internal calculations and data tables to
decide how much fuel to add to the incom-
ing air. It uses sensors such as the coolant
temperature sensor (CTS), the throttle
position sensor (TPS), and the manifold
absolute pressure sensor (MAP) to deter-
mine optimum mixtures. The important
difference here is that it does not check to
see if the mixtures are correct, leaving the
computer adjustment loop open.
• Intake Manifold Vacuum
• Throttle position
• RPM
• Incoming Air Temperature
• Volume of Incoming air
• Air Fuel Ratio, in percentage ( % )
In many vehicles, the computer controls
other systems related to open and closed
loop modes, including idle speed, elec-
tronic spark control, exhaust gas recircula-
tion, and transmission torque converter
clutches.Inopenloopmode,someofthese
systemswillbeadjustedtospeedthewarm-
ing of the engine and get the computer into
closed loop mode as quickly as possible.
Fuel injection is somewhat more sophis-
ticated in the way it delivers fuel. The
computerstilladdsanappropriateamount
of fuel to the entering air, but now it uses
fuel injectors (either in a throttle body or at
each intake port). Fuel injectors are far
more precise than carburetor jets, and
create a much finer fuel “mist” for better
combustion and increased efficiency. In
addition, most fuel injection systems have
ways of measuring exactly how much air
is entering the engine, and can calculate
the proper air/fuel ratio using lookup
tables. Computers no longer have to “es-
timate” how much air the engine is using.
INPUT
SENRS
OBD II: The Next Horizon
ORS
T
In1994,manymanufacturersbeganequip-
ping cars with a new class of computer
technology which puts more processing
power under your dash than ever before. It
is called On-Board Diagnostics, Second
Generation, or OBD-II. It is required on all
vehicles sold in the US beginning January
1, 1996 (though most domestic manufac-
turers introduced it earlier than required),
and offers increased system monitoring
and diagnostic information. This new sys-
tem will store a library of 400 general
trouble codes and another 400 manufac-
turer-specific codes. These codes cover
Body Systems (B-Codes), Chassis Sys-
tems(C-Codes),andPowerTrainSystems
TUA
BRAINS OF THE
AC
In closed loop mode, the computer still
decides how much fuel to add by using the
sensors listed above, and by looking up
the appropriate numbers on a data table.
However, it now checks itself to determine
whether the fuel mixture is correct. It is
able to check itself by using the informa-
tion provided by the oxygen sensor(s)
(O2S) in the exhaust manifold. The oxy-
gen sensors will tell the computer if the
engine is running rich or lean, and the
computer can take steps to correct the
situation. Inthisway, thecomputer closes
the adjustment loop by checking itself and
making necessary corrections. It should
be noted that the O2 sensors must be at a
very high operating temperature (approxi-
mately 650° F) before they will begin to
feed information back to the computer.
This is why open loop mode is neces-
COMPUTER
In many modern systems, the computer
also uses information provided by sen-
sors to give it an idea of how well it is doing
itsjob, andhowtodoitbetter. Sensorscan
tell the computer how warm the engine is,
how rich or lean the fuel mixture is, and
whether accessories (like the air condi-
tioner) are running. This feedback infor-
mation allows the computer to “fine tune”
the air/fuel mixture, keeping the engine
operating at its peak.
Switches and Actuators are electric de-
vices energized by the computer to allow
commands to perform a specific function.
Switches are often called relays (such as
the coolant fan switch). Actuators might
include solenoids (such as fuel injector
valves) and small motors (such as the Idle
Speed Control). Not all of the computer’s
outgoing signals are routed to switches
and actuators. Sometimes information is
sent to other system computers like trans-
mission, brakes, ignition modules, and trip
computers. Signals running from the PCM
to other components are called “outputs.”
What the Computer needs to know:
• Engine operating condition. Sensors
used are: coolant temperature, throttle
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(P-Codes). Now, basic terms are standard-
ized and all generic codes will share a
common format and terminology that the
manufacturers and the Society of Auto-
motive Engineers (SAE) designed. You
will be glad to know that as your car gets
smarter, it will be easier for you to keep
track of what is going on under the hood.
servicing a particular trouble code take
into account all the possibilities. If you
follow these procedures, you should be
able to find the problem causing the code
and fix it yourself.
Trouble Codes and Diagnostics help
you fix the problem
To find the cause of the problem yourself,
you need to perform special test proce-
dures called “diagnostics.” These proce-
dures are in the vehicle service manual,
and your scan tool makes it easy to locate
and diagnose malfunctioning systems.
There are many possible causes for any
problem. For example, suppose you
turned on a wall switch in your home and
the ceiling light did not turn on. Is it a bad
bulb or light socket? Are there problems
with the wiring or wall switch? Maybe
there is no power coming into the house!
As you can see, there are many possible
causes. The diagnostics are written for
Actron makes it easy to fix computer-
controlled vehicles
Using the Actron scan tool to obtain
trouble codes is fast and easy. Trouble
codes give you valuable knowledge -
whether you go for professional service or
do it yourself. Now that you know what
trouble codes are and where they come
from, you are well on your way to fixing
today’s computer-controlled vehicles!
2-2 About Codes
Where do Trouble Codes come from and what are they for?
Engine computers can find problems
Code numbers reveal test results
The computer systems in today’s vehicles
do more than control engine operations—
they can help you find problems, too! Spe-
cial testing abilities are permanently pro-
grammed into the computer by factory
engineers. These tests check the compo-
nents connected to the computer which
are used for (typically): fuel delivery, idle
speed control, spark timing, emission sys-
tems, and transmission shifting. Mechan-
ics have used these tests for years. Now
you can do the same thing by using your
Actron scan tool!
The test results are stored by using code
numbers, usually called “trouble codes”
or“diagnosticcodes.”Forexample,acode
22 might mean “throttle position sensor
signal voltage is too low.” Code meanings
are a part of your scan tool’s software—all
you have to do is look them up! But since
code definitions vary with manufacturer,
model year, and engine, you may also
want to refer to a vehicle service manual
for additional information. These manu-
als are available from the manufacturer,
other publishers, or your local public li-
brary. See page 2 for more information on
ordering service manuals.
2-3 When to Read Codes
Many vehicles have a “Malfunction Indicator Lamp” or MIL, which has been referred to
as a “Check Engine” light in the past. With the advent of OBD-II, all engine trouble lights
are now called “Malfunction Indicator Lamps” or MIL.
UsetheMalfunctionIndicatorLamptotellyouwhentroublecodeshavebeen
stored in memory:
About the Malfunction Indicator Lamp
Enginecomputersperformspecialtests
• “Check Engine”
The engine computer runs the special
tests, depending on the manufacturer,
engine, model year, etc. There is no “uni-
versal”testthatisthesameforallvehicles.
The tests examine INPUTS (electrical sig-
nals going INTO the computer) and OUT-
PUTS (electrical signals coming OUT of
the computer), as well as internal calcula-
tions made by the computer. Input signals
which have “incorrect” values, or output
circuits which do not operate properly are
noted by the test program and the results
are stored in the computer’s memory.
These tests are important. The computer
cannot control the engine properly if it has
incorrect input information or faulty output
circuits.
• “Service Engine Soon”
• “Service Engine Now”
Read Trouble Codes with the scan tool
You can obtain trouble codes from the
engine computer memory by using the
scan tool. You can also monitor the opera-
tion of systems throughout the vehicle,
helpingtopinpointthesystemwherethere
may be a problem. Once you have read
the trouble codes, you can either:
• marked with a small engine picture or
diagram
The Malfunction Indicator Lamp is nor-
mally OFF when the engine is RUNNING.
MalfunctionIndicatorLamp:
normal operation
NOTE: The Malfunction Indicator Lamp
will turn on when the ignition key is in ON
position, but the engine is OFF prior to
starting the vehicle. This is a normal test of
all the dashboard message lights.
• Have your vehicle professionally ser-
viced.
The engine computer turns the Malfunction
Indicator Lamp on and off as needed. This
dashboard message is either amber or
red and labeled:
Or,
• Repair the vehicle yourself using the
trouble codes to locate the source of the
problem.
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MalfunctionIndicatorLamp:
problem spotted
Poorly running engine, no Malfunction
Indicator Lamp
Section 3: Actron Help
If the Malfunction Indicator Lamp does not
come on, you may have an electrical prob-
lem which needs repair. Refer to the “Di-
agnostic Circuit Check” steps in the “Basic
Diagnostic Procedures” section of your
vehicle service manual.
Most likely, this condition is not due to
computer system failures, but reading
codes can still be useful as part of a basic
trouble-shooting procedure. Check wir-
ing and bulb for “Check Engine” light
failures. Refer to vehicle service manual
for additional diagnostic information.
3-1 Tool Problems
There may be times when your scan tool
does not seem to be communicating with
the vehicle. It is possible that the vehicle’s
computer will stop communicating, but for
the most part, if you loose the “link,” you
should check the vehicle power adapter
and the cigarette lighter circuit first. Since
the scan tool has built-in diagnostics, it is
easytoisolateaproblemwiththeScanTool
itself. There will be two basic types of
problems that you will deal with: vehicle
problems and tool problems. Both might
affect your test. Remember, the scan tool
always goes through a SELF CHECK
each time you power the unit up, before
testing. Use the trouble-shooting tips be-
low to help diagnose scan tool problems
before calling Actron’s Technical Support
line:
thevehiclecigarettelighterreceptacle.
2. Toolwillnot“Link”tothevehiclecom-
puter:
A. Unplug the vehicle Data Link Connec-
tor (DLC) adapter and plug it back in to
verify that it is properly plugged into the
vehicle DLC.
MalfunctionIndicatorLamp:
intermittent problem
IMPORTANT: Some vehicles may not be
equipped with Malfunction Indicator
Lamps.Somemid-80’sFords,forexample,
did not use a Malfunction Indicator Lamp
to warn of problems. On vehicles without
Malfunction Indicator Lamps, it is more
difficult to recognize problems. Some
symptoms of a computer- or sensor-
related problem might be:
When the light remains ON after the en-
gine is RUNNING:
B. Review the vehicle VIN information and
verify that you have properly entered
the correct vehicle VIN information in
the scan tool setup. Also review the
Actron supported vehicle list (found in
scan tool Application Cartridge
manual).
• The computer sees a problem that does
not go away (known as a “current” fail-
ure).
• The light will stay on as long as the
problem is present.
• A trouble code is stored in computer
memory (a “history” or “memory” code).
C.In some GM cars, if there is a Trouble
Code set that refers to the internal
MEMCAL-PROM, you may not get a
vehicle data stream.
• Hard starting
• Poor idle quality
• Use the scan tool at the earliest conve-
nient time to obtain codes.
• Poor fuel mileage
• Misfiring or hesitation
• Black or dark gray smoke from tailpipe
• Failure of emissions tests
When the light comes ON, then goes OFF
while the engine is running:
1. The scan tool will not power-up:
3. Your scan tool will not record data:
• The computer saw a problem, but the
problem went away (known as an “in-
termittent” failure).
A. Check the cartridge – Is it properly
seated?
A. Take time to review the vehicle applica-
tion manual for the vehicle that you are
working on. Refer to the data recording
section, following the instructions and
try again.
In vehicles without a Malfunction Indicator
Lamp, it is important to be alert to any
warningsignsofcomputersystemtrouble.
This is why the scan tool is so valuable.
With it, you can diagnose any vehicle’s
electronic systems, regardless of whether
the vehicle is equipped with a Malfunction
Indicator Lamp. It is also important to note
that vehicles without Malfunction Indica-
tor Lamps DO store trouble codes just like
any other computer-controlled vehicle.
Reading codes is still a very important part
of diagnosing problems on these vehicles.
B. Check the cigarette lighter for power.
Take the cigarette lighter element and
plug it in to verify that it is heating up. If
not, check lighter fuse.
• A trouble code is stored in computer
memory (a “history” or “memory” code).
• The light went out because the problem
went away, but the code stays in
memory.
B. Verify that the scan tool memory buffer
is not already full.
C.UN-plug and plug back in to verify the
cigarettelighterendisproperlyseatingin
C.Use the scan tool self-test and verify
that the on-board RAM memory is okay.
• Use the scan tool at the earliest conve-
nient time to obtain codes.
NOTE: The computer will automatically
erase these codes after several restarts if
the problem does not return.
4. YourKeyboarddoesnotfunctionprop-
erly:
NOTE:OnvehiclesequippedwithOBD-II,
the Malfunction Indicator Lamp also sig-
nals an emissions-control related failure.
The vehicle may not run any differently,
but the OBD-II system is designed to note
very small changes in the engine’s opera-
tion which could lead to emissions dam-
age or failure.
A. Perform the Keyboard Test by entering
the Self-Test and select the Keyboard
Test function. This will test out all but-
tons along with the sound alert.
B. If the keyboard test shows nothing
and you still experience the problem,
thencallActron’s technical supportper-
sonnel at 1-800-ACTRON-7.
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The screen below is how the Tool Self-
Tests option appears on the Function List
(NOTE: This is a GM Function List. Func-
tion Lists for other manufacturers may
differ slightly):
done. If you selected Tool Self-Test from
the Function List, then press the FUNC-
TIONkeytoreturntothefunctionlistatany
time.
3-2 Car Problems
tion PROM matches the vehicle setup.
Some GM vehicles have had replace-
ment PROMs installed from newer ve-
hicles to correct driveability problems.
Check the scan tool Application Car-
tridge manual for applicable models
and years.
If your scan tool is having difficulty “link-
ing” with the vehicle computer, be sure
that you have double checked all scan
tool interfaces, including the power con-
nectors and the DLC connection. When
you are sure that the scan tool is not
malfunctioning (run scan tool Self-Tests),
then the problem may be with the vehicle’s
electrical system or with the vehicle com-
puter itself. Check the following:
GMFunctionList
7)Tool Setup
8)ToolSelf-Test
9)CodeLookup
• Make sure the vehicle’s on-board com-
puter has a good ground. If your
vehicle’s on-board computer has a
ground going directly to the computer’s
case, then clean up this connection
and apply a conductive grease to the
mating surfaces.
NOTE: The beeper is disabled while the
Display Test Screen is visible. Therefore
any key press will not register a beep.
ToselectToolSelf-Testsoneitherscreen,
use the UP and DOWN arrow keys to
move the cursor so it is pointing to the Tool
Self-Tests option, then push the ENTER
key to select this option.
• If you are using the cigarette lighter
power adapter, verify that the vehicle’s
cigarette lighter and fuse are OK.
Keyboard Test
The Keyboard Test is used to check the
functionality of the scan tool’s keyboard.
After you select Keyboard Test from the
Tool Self-Test Menu, the Keyboard Test
screen with instructions is displayed.
• If the cigarette lighter adapter is used to
power-up the scan tool, then make sure
the vehicle’s battery has a minimum 8
volt charge. The scan tool requires a
minimum of 8 volts to power-up.
After selecting the Tool Self-Tests option,
you will be given a menu of scan tool self-
tests to choose from:
• On some carbureted engines, the igni-
tion key must be ON and the engine
OFF in order to establish communica-
tion between the scan tool and the
vehicle’s on-board computer. If the en-
gine was running when the Operating
Error occurred, then turn the ignition
key OFF and then ON, but do not start
the engine.
Tool Self-Test
1)DisplayTest
2)KeyboardTest
3)Memory Test
PushButtonToTest
KeyAndDisplay
NameKey:
• Verify the ignition key is ON and not in
the accessories (ACC.) position.
BACKUPWhenDone.
• Check the vehicle’s on-board computer
for a blown PCM fuse. The PCM fuse is
located on the fuse block in the passen-
ger compartment. If the PCM fuse is
blown, the vehicle’s on-board computer
cannot transmit data.
From the above menu, use the UP and
DOWN arrow keys to move the cursor so
it is pointing to the Self-Test option of your
choice, thenpushtheENTERkeytoselect
this option.
Eachtimeyoupressakey,checkscantool
display. The key name should appear and
the scan tool should beep. For example,
if you press the UP arrow, the screen will
display “Key: UP ARROW.” If the button
name is not displayed, the key is not
working.TheonlyexceptionistheBACKUP
key. When the BACKUP key is pressed,
the scan tool returns to the Tool Self-Test
Menu. If you are not returned to the Tool
Self-Test Menu, then the BACKUP key is
not working. NOTE: The FUNCTION key
will not return you to the Function List
while you are keyboard testing.
• As a last resort, the vehicle’s on-board
computer or calibration PROM may be
defective.Checkvehicleservicemanual
to determine correct computer tests for
your particular vehicle.
• Check to be sure your vehicle’s calibra-
Display Test
After you have selected Display Test as
your choice, a screen detailing the test is
displayed. The Display Test will fill every
pixel of the ScanTool’s LCD display with
a solid black character. Press ENTER to
display solid black characters.
3-3 Scan Tool Self-Tests
sible during scan tool power-up. If a key-
board problem happens while you are
Viewing Data, it is easier to run a Key-
board Self-Test from the Function List
than to remove and then re-apply power
to the scan tool.
Scan tool Self-Tests are used to test the
operation of the scan tool’s display, key-
board, and internal memory. The Tool
Self-Tests menu can be accessed when
the scan tool is initially powered-up, and
from the Function List. Convenience is the
reason the Tool Self-Tests menu is acces-
sible in two ways. If the scan tool has a
display problem on power-up, you do not
want to enter vehicle set-up information
just to get to the Function List to run the
Display Self-Test. It is far more convenient
to have the Tool Self-Tests menu acces-
ENTERToTest.Look
ForMissingSpots
InDisplay.Press
Memory Test
The scan tool has already run a Memory
Self-Test during power-up. It is assumed
thatthescantoolpassedtheMemorySelf-
Test on power-up, because you should
not have proceeded any farther if it failed.
Once you have reached the Function List,
the scan tool may have trouble playing
After the ENTER key is pressed, the dis-
play on power-up looks like this:
BACKUPWhenDone
The Display Test Screen is shown below.
Look for pixels that are not black. In other
words, look for missing spots in the solid
black characters. Press the BACKUP key
to return to the Tool Self Test Menu when
SelectFunction
1)NewVehicle
2)ToolSelf-Test
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back recorded data, displaying trouble
code definitions, or doing any other func-
tion that uses the scan tool’s internal
memory. If this happens, it is a good idea
to run the Memory Test again. From the
Tool Self-Test Menu, select the Memory
Test option. A “working please wait” mes-
sage is displayed while the scan tool tests
its internal memory:
played. Press the ENTER key to return to
the Tool Self-Test Menu.
4-2 Call Actron
4-3 E- Mail &
Internet Address
Actron is also available electronically for
comments and ordering information.
Actron’s E-Mail address is:
In addition to your local dealer, all Actron
equipment and replacement parts are
available directly from the Actron factory.
Product catalogs, pricing information, and
replacement components can be ordered
by contacting Actron directly.
MemoryTestFailed
PressENTERToCont
MemoryTestPassed
PressENTERToCont
And while you’re on-line, be sure to check
out Actron’s Website, where you’ll find
equipmentinformation, newproducts, and
technical tips to help you make the most of
your new Actron ScanTool.
By US mail:
Actron Manufacturing Company
15825 Industrial Parkway
Cleveland, OH 44135, USA
Working
**PleaseWait**
By phone:
1-800-228-7667
On the World Wide Web:
NOTE: If you selected Tool Self-Test from
theFunctionList,thenpresstheFUNCTION
key to return to the function list at any time.
When the Memory Test is completed,
either a “Memory Test Failed!” or a
“Memory Test Passed!” message is dis-
By fax:
(216) 651-2388
For Technical Support call:
1-800-ACTRON-7
Section 4: Accessories and How to Order
4-1 Where to Buy
Actron offers a complete line of high qual-
ity automotive diagnostic and repair
equipment. Additional cartridges, cables,
connectors, and adapters for the scan
tool are available from the local retail
store where you originally purchased
your scan tool. The table below lists the
scan tool accessories.
Actron
Actron
Kits:
Model Number Replacement Parts:
Part Number
GM OBD II cable kit
CP9115
CP9116
CP9120
CP9117
CP9118
CP9119
Cigarette power cable
Carrying Case
Main Tool operators manual
GM cartridge manual
Ford cartridge manual
Chrysler cartridge manual
38-1908
400-2080
2-218601
2-218301
2-218401
2-218501
Ford Probe MECS cable kit
Chrysler L-H engine cable kit
Chrysler OBD II cable kit
Battery Clip Adapters
AC power converter 110/12V
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vehicles. This information is used to design and
build aftermarket diagnostic equipment.
then the duty cycle is 25%. A duty cycle of 0%
means the signal is always at a “low” value and
not changing. A duty cycle of 100% means the
signal is always at a “high” value and not chang-
ing. The PCM uses duty cycle type signals when
it wants more than just “on-off” control of an
actuator. This is how it works: A 50% duty cycle
signal going to a vacuum switching solenoid
means the solenoid will be “on” (passing full
vacuum) half the time, and “off” (passing no
vacuum) half the time. The average amount of
vacuum passing through the solenoid will be one
half the full value because the solenoid is only
“on” for half the time. This signal changes at a
rapid rate, as often as ten times per second. Thus
the PCM can get a vacuum controlled actuator to
move halfway between “no vacuum” and “full
vacuum.” Other positions can be achieved by
changing the duty cycle of the control signal
which in turn changes the average amount of
control vacuum.
Section 5: Glossary of Terms
Detonation: Uncontrolled ignition of the air/fuel
mixtureinthecylinder.Alsoreferredtoas“knock,”
detonation indicates extreme cylinder pressures
or “hotspots” which are causing the air/fuel mix-
ture to detonate early. High cylinder pressures
may be caused by excessive load (trailer towing,
A/C operation, etc.) or by too much spark ad-
vance. High octane fuel has a higher resistance
to uncontrolled ignition, and may be used to
control detonation when the PCM is unable to
retard timing sufficiently to prevent it from occur-
ring. NOTE: High octane fuel is not a cure for the
problem, only the symptom. If your vehicle expe-
riences long-term detonation, check for other
causes.
Actuator: Devices that are powered by the PCM
ClosedLoop(C/L):Thisiswhenacontrolsystem
performs an action (expecting a certain result),
then checks the results and corrects its actions
(ifnecessary)untilthedesiredresultsareachieved.
Example: Fuel delivery. The PCM operates a fuel
injector in a way that should deliver an optimum
air/fuel mixture, as long as everything in the fuel
system is operating as expected. In closed loop
operation, the PCM uses the oxygen sensor to
check the results (fuel delivery may be different
than expected because of variations in fuel
pressure or injector operation). If the oxygen
sensor indicates a “rich” condition, the PCM will
compensate by reducing fuel delivery until the
oxygen sensor signals an optimum air/fuel mix-
ture. Likewise, the PCM will compensate for a
“lean” condition by adding fuel until the oxygen
sensor once again signals an optimum air/fuel
mixture.
to control things. Actuator types include relays,
solenoids, and motors. Actuators allow the PCM
to control engine operation.
A/F: Air/Fuel ratio. This refers to the proportion of
air and fuel delivered to the cylinder for combus-
tion. For example, if you have 14 times more air
than fuel (by weight) then the A/F ratio is 14:1
(read as “fourteen to one”). The ideal operating
A/F ratio in an automotive application is 14.7:1.
Check Engine Light (CEL): The “Check Engine”
light (CEL) will illuminate when the PCM detects
a circuit malfunction in any of the engine feed-
back circuits. When the malfunction occurs, the
CEL will remain lit as long as the PCM detects the
circuit problem. This will automatically set and
store a trouble code in the PCM’s memory. Some
manufacturersalsorefertotheCELasaMalfunc-
tion Indicator Light (MIL), or the Emissions Main-
tenance Lamp (EMR) on some Chrysler trucks.
Diagnostic Trouble Codes: Diagnostic Trouble
Codes (DTC) indicate a malfunction flagged by
the PCM. The PCM will display a corresponding
numerical code number based on a look-up table
in the program of the on-board computer. De-
pending on the manufacturer, the number of
DTCs vary by vehicle and supported systems.
Most systems have the ability to store codes in
memory, which are commonly referred to as
“history codes” or “soft codes.” Malfunctioning
circuits will generate continuous Check Engine
lamp illumination, called “current codes” or “hard
codes.” History codes, based on the
manufacturer’sdiagnosticstrategy,willbecleared
from the PCM’s memory after several ignition
circuitstartcyclesifthecircuitdoesnotreflectthe
failure again. This capability does allow the
technician to access some information on which
circuits were malfunctioning at a previous point.
OBD-II systems will transmit many more DTCs
than the past systems, and therefore will allow a
technician the ability to better pin-point failures
and past events. They only way to clear codes on
OBD-II systems will be with a scan tool that has
the proper programming to perform the function.
DVM: Digital Volt Meter. An instrument using a
numeric readout to display measured voltage
values as opposed to a moving needle on a
gauge face. Usually the instrument has other
measuring capabilities, such as resistance and
current, and may be called a Digital Multi-Meter
(DMM). Most DVMs have 10 Megaohm input
impedance. This means the circuit under test will
not be electronically disturbed when the DVM is
connected for a measurement.
Thus, closed loop operation means the PCM can
“fine tune” control of a system to achieve an exact
result providing the PCM has a means to check
results (like an oxygen sensor).
C3 or CCC: Computer Command Control. The
name of the General Motors electronic engine
control system used on most vehicles built since
1982.,
Data Link Connector (DLC): The Data Link
Connector (DLC) is a universal term for the
interface port between the vehicle’s on-board
computer and the ScanTool. It is sometimes
referred to as the Assembly Line Diagnostic Link
(ALDL), Vehicle Interface Port (VIP), or Serial
Communication Interface (SCI). The DLC is able
to transmit PCM data to the ScanTool as it is
processed. The DLC may be located in the
engine compartment or in the passenger com-
partment, depending on manufacturer. DLC de-
sign also varies from manufacturer to manufac-
turer, ranging from a 6-pin to a 17-pin connector
interface. All vehicles with OBD-II use a 16-pin
connector located in the passenger compart-
ment. The ScanTool requires manufacturer-spe-
cificadaptercablestolinkwithnon-OBD-IIDLCs.
ChryslerSerialCommunicationInterface(SCI):
This is Chrysler’s vehicle adapter (or Data Link
Connector) used to link scan tools with the PCM.
EarlyChryslerOBDsystems(1981-83)broadcast
trouble codes, but gave no operating parameter
data. In 1983, the second phase of Chrysler
OBD, called the Serial Communication Interface
(SCI), was introduced with expanded serial data
and many test modes for the technician to access
with a scan tool. SCI provides the following
modes to access vehicle data: Diagnostic Test
Mode, CircuitActuationTestMode(ATM), Switch
Test Mode, Sensor Test Mode, and Engine
Running Test Mode. Each of these modes allow
for different procedures of diagnostic tests and
test routines. These routines are programmed
into the Chrysler Logic Module (LM) which then
passes the information on to the power module
or Single Board Engine Controller (SBEC). The
vehicle diagnostic adapter is located in the en-
gine compartment on the right-hand side, next to
the SBEC unit with a dust cap marked “Diagnos-
tic.”
ECM: Electronic Control Module. The “brains” of
the engine control system. It is a computer
housed in a metal box with a number of sensors
and actuators connected with a wiring harness.
Its job is to control fuel delivery, idle speed, spark
advancetiming, andemissionsystems. ThePCM
receives information from sensors, then ener-
gizesvariousactuatorstocontroltheengine. The
ECM is frequently called the PCM (Powertrain
ControlModule)invehicleshavingothercomputers.
These other computers are used for climate
control, entertainment systems, transmissions,
etc.
DIS: Distributorless Ignition System or Direct
Ignition System. A system that produces the
ignition spark without the use of a distributor.
Data Stream:Thisistheactualdatacommunica-
tions broadcast from the vehicle’s PCM to the
diagnostic connector. The individual manufac-
turers determine the number of “data bytes” a
specific engine will broadcast. The size of the
data stream is usually dependent on the com-
plexity of the engine, transmission, ABS, and
other systems supported by the PCM. All manu-
facturers supply program documents for each
year, engine, and option combination that a
particular PCM supports in all the manufacturer’s
EFI: Electronic Fuel Injection. A term applied to
any system where a computer controls fuel deliv-
ery to the engine by using fuel injectors.
Duty Cycle: A term applied to frequency signals
— those which are constantly switching between
a small voltage value (close to zero) and a larger
value (usually 5 volts or more). Duty cycle is the
percentage of time the signal has a large voltage
value. For example, if the signal is “high” (large
voltage) half of the time, the duty cycle is 50%.
If the signal is “high” only one fourth of the time,
Engine Parameters: This is the translated infor-
mation that is displayed on the scan tool screen.
Parameters will include the information inputs
and the output signals from the PCM.
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ESC: Electronic Spark Control. This is an ignition
system function that works on vehicles having a
knock sensor mounted on the engine block. The
knock sensor is wired to circuitry in a separate
module (early version) or inside the PCM (later
versions). If the sensor detects engine knock, the
ESC function alerts the PCM which will immedi-
ately retard the spark to eliminate the knocking
condition.
Functional Tests: These are tests of PCM-
controlled systems, such as the fuel pump, the
“Check Engine” light, and other switches and
actuators. Functional Tests are generally depen-
dent on the vehicle manufacturer’s OBD strategy
and the PCM diagnostic architecture. Functional
tests require that the scan tool have the ability to
perform bi-directional communications with the
vehicle’s PCM. This means that the scan tool
must “talk” to the vehicle’s PCM, instead of just
“listening” to the incoming vehicle data stream.
Examples of functional tests are: Chrysler’s ac-
tuator/switch tests that allow you to review the
operation of a switch as you turn it on or off from
the driver’s seat, and turning the fuel pump on
and off. On a GM vehicle, a functional test is
placing the vehicle in Ground Mode to check the
PCM’s self-test diagnostics and the “Check En-
gine” lamp operation.
makes the element sensitive only to engine
vibrations associated with detonation (“knock-
ing”).
On-Board Diagnostics, Phase II (OBD-II): With
the passing of the 1990 Clean Air Act Amend-
ment, the EPA imposed more stringent require-
ments which include the addition of multiple
oxygen sensors, one before the catalytic con-
verter and one after to provide the PCM with
information on catalyst efficiency and condition.
There are also computer-controlled EGR, fuel
pressure regulators, and smart ignition systems.
Inaddition, OBD-IIrequiresacommondiagnostic
connector and location, as well as an industry-
standard data message, both defined by an
industry committee made up of engineers from
most major manufacturers and the SAE. Vehicle
manufacturers are required by law to provide at
least a minimum amount of data for emissions
programs to access the critical emissions data
available through OBD-II. OBD-II began to ap-
pear in vehicles in late 1994, and is required
equipment on all cars sold in the US after January
1, 1996.
MFI: Multi-Port Fuel Injection. See “MPFI” defini-
tion.
MIL: Malfunction Indicator Lamp. Also known as
a Check Engine Light or CEL.
Mode:Atypeofoperatingcondition, suchas“idle
mode” or “cruise mode.”
EST:ElectronicSparkTiming. Anignitionsystem
where the PCM controls the spark advance
timing. A signal called EST goes from the PCM to
the ignition module which fires the spark coil. The
PCM determines optimum spark timing from sen-
sor information – engine speed, throttle position,
coolant temperature, engine load, vehicle speed,
Park/Neutral switch position, and knock sensor
condition.
MPFI: Multi-Port Fuel Injection. A fuel injection
system using one (or more) injector(s) for each
cylinder. The injectors are mounted in the intake
manifold, and fired in groups rather than individu-
ally.
M/T: Manual transmission or manual transaxle.
NOx: Oxides of Nitrogen. A pollutant. The EGR
system injects exhaust gases into the intake
manifold to reduce these gases at the tailpipe.
FBC: Feedback Carburetor. This is used on early
versions of computer-controlled engines. It is a
carburetor which can have its fuel delivery modi-
fied by an electronic signal from the PCM. The
signal controls a mixture control solenoid (MCS)
attached to the carburetor body.
Ground: The return path for current to flow back
to its source (Usually the negative battery termi-
nal). It is also the reference point from which
voltage measurements are made (the connec-
tion place for the negative (-) test lead from a
voltmeter).
Open (Circuit): A break in the continuity of a
circuit such that no current may flow through it.
On-BoardDiagnostics(OBD):Asvehiclemanu-
facturers developed on-board diagnostics for
their service procedures and to meet EPA regu-
lations, the first phase of this computerization
was referred to as OBD. This technology started
in the late 1970’s and carried through to the early
1980’s. Most of these early systems were very
crude, especially when compared to today’s
OBD. Manyrequiredamanufacturer-specifictool
to read trouble codes and other computer infor-
mation. This technology used a feedback loop
system to monitor exhaust emissions and pro-
vided computer control of the vehicle’s fuel
system.
OpenLoop(O/L):Thisiswhenthecontrolsystem
performs an action (expecting a certain result),
but has no way of verifying if the desired results
were achieved. Example: The PCM operates a
fuel injector expecting a certain amount of fuel to
bedelivered(ThePCMassumeseverythinginthe
fuel system is performing properly). In open loop
operation, the PCM has no way of checking the
actual amount of fuel delivered. Thus, a faulty
fuel injector or incorrect fuel pressure can change
the amount of fuel delivered and the PCM would
not know it.
Ford Electronic Engine Control IV (EEC-IV):
This is the name of Ford’s Powertrain Control
Module (PCM) used in all Ford cars and trucks
since the mid-1980’s. It is designed to be read by
aftermarket scan tools. Earlier versions of this
PCM were referred to as EEC-I, EEC-II, or EEC-
III, and were only accessible by the dealer via a
specific diagnostic tool. On carbureted vehicles,
Ford used a system called the Microprocessor
ControlledUnit(MCU),whichisaccessiblethrough
an adapter similar to the EEC-IV’s. Other varia-
tions of the EEC-IV vehicle adapter are used on
Ford’shybridvehicles,suchastheProbeandsome
Escort/Tracer models, which use Mazda PCMs
and have different protocols and codes. Informa-
tion on these vehicles is widely available, and
most scan tools support these vehicles as well as
the standard Ford EEC-IV systems. Ford’s diag-
nostic strategy offers several avenues to access
codes and test procedures.
Inputs: Electrical signals running into the PCM.
These signals come from sensors, switches or
other electronic modules. They give the PCM
information about vehicle operation.
KOEO: Key On, Engine Off. A test mode where
the PCM is active and feeding data parameters,
but the engine is not running. Because the
engine is not running, some data parameters
may not be accurate or available in this mode. On
Ford vehicles, KOEO testing is the only way to
read memory codes stored in the PCM.
On-Board Diagnostics, Phase I (OBD-I): By
1985, theCaliforniaAirResourcesBoard(CARB)
had called for more uniform diagnostic systems
to be used on vehicles sold in California. Com-
bined with federal exhaust emission regulations
enacted in the early 1990’s, CARB required that
all vehicles sold in California have an integrated
PCM structure that monitored all critical emis-
sions components. Manufacturers found that it
wassimplertoincorporatethissystemintoalltheir
vehicles built in the USA. In fact, by the end of
1986, most diagnostic procedures were uniform
within each manufacturer, providing an opportu-
nity for generic scan tools to come to market for
the home mechanic.
In general, a control system operates in open
loop mode only when there is no practical way to
monitor the results of an action. Example: Fuel
delivery during cold engine warm-up. The com-
puter runs in open loop mode because the
oxygen sensor is not hot enough to send a signal.
Without the sensor signal, the computer cannot
check the actual amount of fuel delivered.
KOER: Key On, Engine Running. A test mode
wherethePCMis activeandfeedingdataparam-
eters, and the engine is running. Since the
engine is running, most data parameters should
be available and accurate.
Knock: See “Detonation.”
Knock Sensor: This sensor is used to detect
engine detonation (or “knock”). When spark
knock occurs, the sensor emits a pulsing signal.
Depending on the vehicle, this signal either goes
to the PCM or a separate ESC (Electronic Spark
Control) module. Then the spark advance is
retarded until detonation stops. The sensor
contains a piezoelectric element and is threaded
into the engine block. Vibrating the element
generates the signal pulse. Special construction
O2S: Oxygen Sensor. The oxygen sensor is
threaded into the exhaust manifold, directly in the
stream of exhaust gases. The PCM uses the
sensor to “fine tune” fuel delivery. The sensor
generates a voltage of 0.6 to 1.1 volts when the
exhaust gas is rich (low oxygen content). The
voltage changes to 0.4 volts or less when the
exhaust gas is lean (high oxygen content). The
sensor only operates after it reaches a tempera-
ture of approximately 349°C (660°F).
Fuel Injector: An electronically controlled flow
valve.Fuelinjectorsareconnectedtoapressurized
fuelsupply(fuelpressureiscreatedbyafuelpump).
Noflowoccurswhentheinjectorisoff(notenergized).
Whentheinjectorisenergized,itopensfully,allowing
fueltoflow.ThePCMcontrolsfueldeliverybyvarying
theamountoftimetheinjectorsolenoidsareturnedon.
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Outputs: Electrical signals sent from the PCM.
These signals may activate relays or other actua-
tors for control purposes throughout the vehicle.
The signals can also send information from the
PCM to other electronic modules, such as the
ignition or trip computer.
Solenoid: Adevicetoconvertanelectricalsignal
to mechanical movement. It consists of a coil with
a wire with a moveable metal rod in the center.
When the power is applied to the coil, the
resulting electromagnetism moves the rod and
performs some mechanical action. The PCM
often uses solenoids to switch vacuum lines on
and off. This allows the PCM to control vacuum
operated devices such as the EGR valve. Fuel
injectors are operated by another type of sole-
noid.
VIN: Vehicle Identification Number. This is the
factory-assignedvehicleserialnumber.Thisnum-
ber is stamped on a number of locations through-
out the vehicle, but the most prominent location
is on top of the dashboard on the driver’s side,
visible from outside the car. The VIN includes
information about the car, including where it was
built, body and engine codes, options, colors,
and a sequential build number. The VIN can also
tell you what adapters you may need to use the
ScanTool with your particular vehicle.
PCM: Powertrain Control Module. The “brains” of
the engine control system. It is a computer
housed in a metal box with a number of sensors
and actuators connected with a wiring harness.
Its job is to control fuel delivery, idle speed, spark
advancetiming, andemissionsystems. ThePCM
receives information from sensors, then ener-
gizes various actuators tocontroltheengine. The
PCMisfrequentlycalledtheECM(EngineControl
Module) in vehicles having other computers.
These other computers are used for climate
control, entertainment systems, transmissions,
etc.
TBI: Throttle Body Injection. A fuel injection
system having one or more injectors mounted in
a centrally-located throttle body, as opposed to
positioning the injectors close to an intake valve
port. Also called Central Fuel Injection (CFI) in
some vehicles.
WOT:Wide-OpenThrottle. Thevehicleoperating
condition brought about when the throttle is
completely (or nearly so) open. The PCM will
typically deliver extra fuel to the engine and de-
energize the A/C compressor at this time for
acceleration purposes. The PCM uses a switch
or the Throttle Position Sensor to identify the
WOT condition.
Thermistor:Aresistorwhoseresistancechanges
with temperature. Thermistors are used as sen-
sorsforvehiclecoolantandmanifoldairtempera-
ture. The resistance decreases as temperature
goes up, sending a voltage signal to the PCM
where it is converted to a temperature measure-
ment.
PROM: Programmable Read-Only Memory. A
small, replaceable electrical component hidden
behind an access door on the PCM. The PROM
contains permanent programming information
the PCM needs to operate a specific vehicle
model. Included are vehicle weight, engine and
transmission type, axle ratio, and other specifics.
ThrottleBody:Adevicewhichperformsthesame
functionasacarburetorinafuelinjectionsystem.
On a throttle body injection (TBI) system, the
throttle body is both the air door and the location
ofthefuelinjectors. Onportfuelinjectionsystems
(PFI, MPFI, SFI, etc.) the throttle body is simply
an air door. Fuel is not added until the injectors
at each intake port are activated. In each case,
the throttle body is attached to the accelerator
pedal.
Relay: A mechanical device for switching high
current circuits on and off. It is electronically
controlled by a low current circuit. Relays allow a
low power PCM signal to control a high power
device such as an electric cooling fan.
ROM: Read-Only Memory. Permanent program-
ming information stored inside the PCM, contain-
ing the information the PCM needs to operate a
specific vehicle model.
Vehicle Adapter: Like General Motors and the
ALDL connector, Ford and Chrysler use Vehicle
Adapter as the name of their diagnostic link. Ford
uses a 7-pin adapter called the EEC-IV self test
adapter. This is generally located in the engine
compartment of Ford vehicles, though specific
location varies (generally it is close to the PCM).
Sensor: Device which gives the PCM informa-
tion. The PCM can only work with electrical
signals. The job of the sensor is to take some-
thing the PCM needs to know, such as engine
temperature, and convert it to an electrical signal
that the PCM can understand. The PCM uses
sensors to measure such things as throttle posi-
tion, coolant temperature, engine speed, incom-
ing air mass and temperature, etc.
Chrysler has a similar adapter for access to the
Serial Communications Interface (SCI) diagnos-
tic program on those vehicles that support SCI.
This adapter is located on the right-hand side of
the engine compartment, and is a 6-pin configu-
ration. This adapter is usually near the Logic
Controller on the SCI computer.
SFI or SEFI: Sequential Fuel Injection or Se-
quential Electronic Fuel Injection. A fuel injection
system that uses one or more injectors for each
cylinder. The injectors are mounted in the intake
manifold, and are fired individually in the same
sequence as the spark plug firing order.
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