check engine light ISUZU TROOPER 1995 Owner's Manual

ENGINE ELECTRICAL 601-1
SECTION 60
ENGINE ELECTRICAL
CONTENTS
Battery . . ..... . ...... . ... . .... . .... ..... .... . .... .. .... . .... . . ... . . . .... . . .. . . .... . ... . ... . .... . . .. ... . .... . . ... . ... . . .. . Section 601
Cranking System
........... ... . ... . .... . .... . . .... . .... .

. ... . . .... . .... . .... . . ... ...
.. .... . . ..... . .... . ......... ... Section 602
Charging System ..... .... . . .............. .... . .... . . .. .. . . ... . . ... . . ... . . ... . . ........ .... . . ..... .. .... . ... . .... . .. Section 603
Ignition System (V6 3.2L) .. .... ...... ...... .. .. .. .... ...... .... .. .... .... .... ...... ...... ...... .......... .... Section 6D4A
SECTION 601
BATTERY
CONTENTS
General Description ............................... 6D1-1
Diagnosis .............................................. 6D1-1
On-Vehicle Service ................................ 6D1-3
Battery Charging ................................ 6D1-3
Jump Starting .................................... 6D1-3
Removal and Installation of The Battery . . 6D1-4
Main Data and Specifications . . . . . . . . . . . . . . . . . . 6D1-4
GENERAL DESCRIPTION
There are six battery fluid caps at the top of the
battery. These are covered by a paper
label.
The battery is completely sealed except for the six
small vent holes at the side. These vent holes per­
mit the escape of small amounts of gas generated
by the battery.
This type
of battery has the following advantages
over
conventional batteries:
1. There is no need to add water during the entire
service
life of the battery.
2. The battery protects itself against overcharging.
The battery
will refuse to accept an excessive
charge. (A
conventional battery will accept an excessive
charge,
resulting in gassing and loss of battery
fluid.)
3. The battery is much less vulnerable to self­
discharge than a conventional type battery.
DIAGNOSIS
1. VISUAL INSPECTION
Inspect the battery for obvious physical damage,
such
as a cracked or broken case, which would per­
mit electrolyte loss.
Replace
the battery if obvious physical damage is
discovered during inspection.
Check
for any other physical damage and correct it
as necessary. If not, proceed to Step 2.
2. HYDROMETER CHECK
There is a built-in hydrometer (Charge test indica­
tor) at the top of the battery. It is designed to be
used during diagnostic procedures. Before
trying to read the hydrometer,
carefully
clean
the upper battery surface.
If your work area is poorly lit, additional light may
be necessary
to read the hydrometer (Fig. 6D1-1).
a. BLUE RING OR DOT VISIBLE -Go to Step
4.
b. BLUE RING OR DOT NOT VISIBLE -Go to
Step 3.

6E2-4 DRIVEABILITY AND EMISSIONS
BASIC KNOWLEDGE REQUIRED
Before using this section of the Service Manual,
there are some areas that you should be familiar
with. Without this basic knowledge, you will have
trouble using the diagnostic procedures
contained in this section.
BASIC ELECTRIC CIRCUITS
You should understand the basic theory of
electricity, and know the meaning of voltage,
amps, and ohms. You should understand what
happens in a circuit with an open or a shorted
wire. You
should be able to read and understand a
wiring diagram. A shortto ground is referred to as
a ground to distinguish it from a short between
wires.
USE OF CIRCUIT TESTING TOOLS
You should know how to use a test light, how to
connect and use a tachometer, and
how to use
jumper wires to by-pass components to test
circuits. Care
should be taken to not deform the
terminal when testing.
USE OF DIGITAL VOLT-OHM METER
(DVOM)
You should be familiar with the Digital Volt-Ohm
Meter, particularly special tool J-39200 or
equivalent. You should be able to measure
voltage, resistance, and current and know how to
use the meter correctly.
The
Digital Volt-Ohm Meter is covered in the
"Special Tools" portion of this section.
DIAGNOSTIC INFORMATION
The diagnostic "Trouble Tree" charts and func­
tional checks in this manual are designed to locate
a faulty circuit or component through logic based
on the process
of elimination. The charts are
prepared
with the requirement that the vehicle
functioned correctly at the time of assembly and
that there are no multiple failures.
The Engine Control Module (ECM) performs a
continual self-diagnosis on certain control
functions. This diagnostic capability is
complemented by the diagnostic procedures
contained in this
manual. The ECM's language for
communicating the source of a malfunction is a
system
of Diagnostic Trouble Codes (DTCs). The
DTC(s) are
two or three digit numbers that can
range from12 to
51. When a malfunction is
detected by the ECM, a DTC is set and the
Malfunction Indicator Lamp is illuminated.
"CHECK ENGINE" MALFUNCTION
INDICATOR
LAMP (MIL)
This light is on the instrument panel and has two
functions:
• It is used to tell the driver that a problem has
occurred, and that the
vehicle should be
taken
for service as soon as reasonably
possible.
• It
is used by the technician to read out
'Trouble Codes" to help diagnose system
problems.
As a bulb and system check, the light will come
"ON" with the key "ON" and the engine not
running. When the engine is started, the light will
turn off. If the light remains on, the self-diagnostic
system has detected a
problem. If the problem
goes away, the light will go out in most cases after
10 seconds, but a Trouble Code will remain stored
in the
ECM.
When the light remains "ON" while the engine is
running,
or when a malfunction is suspected due
to a
driveability or emissions problem, a on-board
diagnostic system check
must be performed. The
procedures
for these checks are given in Section
"A". These checks will expose malfunctions
which may
not be detected if other diagnostics
are performed
prematurely.
INTERMITTENT "CHECK ENGINE"
MALFUNCTION INDICATOR
LAMP (MIL)
In the case of an "intermittent" problem, the
"Check Engine"
malfunction indicator lamp will
light
for ten (1 0) seconds and then will go out.
However, the corresponding
trouble code will be
stored in the
memory of the ECM until the battery
positive
voltage to the ECM has been removed.
When unexpected DTC(s) appear during the
DTC
code reading process, one can assume that these
DTC(s) were set by an intermittent malfunction
and could be helpful in diagnosing the system.
An intermittent
DTC may or may not re-set. If it is
an intermittent failure, a DTC Chart is not used.
Consult the "Diagnostic Aids" on the intermittent
trouble code. Section "B" also covers the topic of
"intermittents". A physical inspection of the
applicable sub-system most often will resolve the
problem.
II

......, .., LU
READING DIAGNOSTIC TROUBLE CODES
(Fig. 6E2-1)
The provision for communicating with the Engine
Control Module (ECM) is the Data Link Connector
(DLC) (See Fig. 6E2-1 ). The DLC is located behind
the
lower front instrument panel. It is used in the
assembly plant
to receive information in checking
that the engine is operating properly before it
leaves the plant. The diagnostic trouble code(s)
(DTCs) stored in the ECM's memory can be read
either through a hand-held diagnostic scannner
plugged into the
DLC or by counting the number
of flashes of the "Check Engine" Malfunction
Indicator Lamp (MIL) when the diagnostic test
terminal
ofthe DLC is grounded. The DLC terminal
"1" (diagnostic request) is pulled "Low"
(grounded) by jumpering to DLC terminal "3",
which is a ground wire. This will signal the ECM
that you want to "flash" DTC(s), if any are present.
Once terminals "1" and "3" have been connected,
the ignition switch
must be moved to the "ON"
position, with the engine not running. At this
point, the
"Check Engine" MIL should flash DTC 12
three times consecutively. This
would be the
following flash, sequence: "flash, pause, flash­
flash,
long pause, flash, pause, flash-flash, long
pause, flash, pause, flash-flash". DTC 12 indicates
that the ECM's diagnostic system is operating.
If
DTC 12 is not indicated, a problem is present
within the diagnostic system itself, and should be
addressed
by consulting the appropriate
diagnostic chart in
DRIVEABILITY AND
EMISSIONS (SECTION 6E2-A).
Following the output of DTC 12, the "Check
Engine" MIL
will indicate a DTC three times if a
DTC is present, or it will simply continue to output
DTC 12. If more than one DTC has been stored in
the
ECM's memory, the DTC(s) will be outputfrom
the lowest to the highest, with each DTC being
displayed three times.
--
Eig tU!2-1-...
DRIVEABILITY AND EMISSIONS 6E2-5
CLEARING TROUBLE CODES
When the ECM sets a trouble code, the "Check
Engine" MIL
will come "ON" and a trouble code
will be stored in memory. If the problem is
intermittent, the light
will go out after 10 seconds,
when the fault goes away. However, the trouble
code
will stay in the ECM memory until the battery
positive voltage
to the ECM is removed.
Removing battery positive voltage
for 30 seconds
will clear all stored trouble codes.
Trouble
Codes should be cleared after repairs
have been completed. Also, some Diagnostic
Charts will tell you to clear the DTC(s) before using
the chart. This
allows the ECM tosetthe DTCwhile
going through the chart, which will help to find the
cause
of the problem more quickly.
wcAUTION:
• To prevent ECM damage, the key must be "OFF"
when disconnecting or reconnecting power to
ECM (for example battery cable, ECM pigtail, ECM
fuse, jumper cables, etc.)
When using a hand-held diagnostic scanner,
or
"Scan tool" to read the DTC(s), clearing the DTC(s)
is done in the same manner as in the above
procedure.
DIAGNOSTIC TEST MODE
When the diagnostic test terminal is grounded
with the ignition "ON" and the engine "OFF", the
system
will enter what is called the Diagnostic
Test Mode.
In this diagnostic test mode the ECM
will:
1. Flash the "Check Engine" MIL "ON" and
"OFF" rapidly (indicating the system is
operating correctly).
2. Display any stored trouble codes by flashing
the
"Check Engine" MIL. Each DTC will be
flashed three times, then
DTC 12 will be
flashed again.
3. Energize all ECM controlled relays and
solenoids except
fuel pump relay. This
allows checking circuits which may be
difficult to energize without driving the
vehicle and being under particular operating
conditions.
4. The idle air control valve moves to its fully
extended position on most models, blocking
the
idle air passage. This is useful in checking
the
minimum idle speed.

6E2-6 DRIVEABILITY AND EMISSIONS
FIELD SERVICE MODE
ENGINE
CONTROL MODULE (ECM)
LEARNING ABILITY
The Engine Control Module (ECM) has a
"learning"
ability which allows it to make
corrections
for minor variations in the fuel system
to improve driveability. If the battery is
disconnected to clear diagnostic codes, or for
repair, the "learning" process has to begin all over
again. A change
may be noted in the vehicle's
performance. To "teach" the vehicle, make sure
the engine is at operating temperature, and drive
at part throttle, with moderate acceleration and
idle conditions, until normal performance returns.
lfthe diagnostic test terminal is grounded with the
engine running, the system is in
"Open" or
"Closed Loop".
In "Open Loop" the "Check Engine" malfunction
indicator lamp flashes
two and one-halftimes per
seconds.
In "Closed Loop", the light flashes once per
second.
Also, in "Closed
Loop", the light will stay "OFF"
most of the time if the system is too lean. It will
stay"ON" mostofthetime if the system is too rich.
While the system is in Field Service Mode, the
ECM will be in the following diagnostic test mode:
1. New trouble codes cannot be stored in the
ECM.
2. The closed loop timer is bypassed.
STANDARD NOMENCLATURE FOR /
CERTAIN ELECTRICAL/ELECTRONIC COMPONENTS AND SYSTEMS /
Starting with the 1993 model, lsuzu Motors will be complying with the Society of Automotive ~ngineers
(SAE) Recommended Practice J 1930. J 1930 is an industry wide standard that was ad6pted into
government regulations and requires certain electrical and electronic components and
syster;ns be known
by the same
nomenclature that have the same function. This standard is also being applied to
abbreviations and acronyms.
This standard is being used in
all 1993 service publications.
To make this standard work, some names and abbreviations are being replaced
with those recommended
by the
SAE Standard. What follows is a partial listing of former ISUZU names and abbreviations besides
the
new ISUZU names and abbreviations.
Former ISUZU Name New ISUZU Name Term
3Gr
Third Gear -3GR
3rd Gear
Third Gear -3GR
4Gr
Fourth Gear -4GR
4th Gear
Fourth Gear -4GR
A/C Air Conditioning -A/C
A/C
Relay Air Conditioning Relay -A/C Relay
Absolute Presure Sensor
Manifofd Absolute Pressure Sensor -MAP Sensor
AC Air Conditioning -A/C
AC Generator . Generator -GEN
ACC Air Conditioning -A/C
Accel
Accelerator Pedal -AP
Accelerator
Accelerator Pedal -AP
ACG Generator -GEN
Air Cleaner Element(s) / Air Cleaner Filter -ACL Filter
Air Cleaner Filter Ele;nent Air Cleaner Filter -ACL Filter
Air Conditioning / Air Conditioning -A/C
Air Injection Reaction System Secondary Air Injection System -AIR System
ALDL Data Link Connector -
DLC
ALDL Diagnostic Connector DLC Diagnostic Connector -DLC Diagnostic Connector ,.
, ....

DRIVEABILITY AND EMISSIONS 6E2-7
Former ISUZU Name New ISUZU Name Term
ALT Generator -GEN
Alternator
Generator -GEN
Assembly Line Communication Link
Data Link Connector -DLC
Assembly Line Data Link
Data Link Connector -DLC
Assembly Link Diagnostic Link
Data Link Connector -DLC
Backpressure Transducer
Backpressure Transducer-BPT
BARO Barometric Pressure -BARO
Baro
Barometric Pressure -BARO
Battery Voltage
Battery Positive Voltage-B+
Battery Voltage Correction Mode Battery Positive Voltage Correction Mode -B+ Correction Mode
Battery Volts
Battery
Positive Voltage-B+
BP Sensor Barometric Pressure Sensor -BARO Sensor
C.E. Light
Malfunction Indicator Lamp -MIL
CAL-PAK Electronically
Erasable Programmable Read Only Memory -
EEPROM
CAL-PAK
Programmable Read Only Memory -PROM
Calibration Pack Electronically Erasable Programmable Read Only Memory -
EEPROM
Calibration Pack
Programmable Read Only Memory-PROM
Cam Angle Sensor Camshaft Position Sensor -CMP Sensor
Cam Sensor Camshaft Position Sensor -CMP Sensor
Camshaft Sensor Camshaft Position Sensor -CMP Sensor
Canister Purge Evaporative Emission Canister Purge-EVAP Canister Purge
Catalytic Converter
Three Way Catalytic Converter-TWC
Check Engine
Malfunction
Indicator Lamp -MIL
Check Engine Indicator Malfunction Indicator Lamp -MIL
Check Engine Light
Malfunction Indicator Lamp-MIL
Code Diagnostic Trouble Code -DTC
Computer Command Control Engine Control Module -ECM
Computer Controlled Coil Ignition Electronic Ignition -El
Controlled Canister Purge Evaporative Emission Canister Purge-EVAP Canister Purge
Converter Three Way Catalytic Converter -TWC
Coolant Engine Coolant -EC
Coolant Level
Engine Coolant Level -ECL
Coolant Level Sensor Engine Coolant Level Sensor -ECL Sensor
Coolant Sensor Engine Coolant Temperature Sensor -ECT Sensor
Coolant Temp. Sensor Engine Coolant Temperature Sensor-ECT Sensor
Coolant Temperature Engine Coolant Temperature -ECT
Coolant Temperature Sensor Engine Coolant Temperature Sensor-ECT Sensor
Coolant Temperature Switch Engine Coolant Temperature Switch -ECT Sensor
Crank RPM Engine Speed -RPM
Crank Sensor Crankshaft Position-CKP

6E2-14 DRIVEABILITY AND EMISSIONS
DATA LINK CONNECTOR ''SCAN TOOLS''
The Engine Control Module (ECM) can communicate a
variety
of information through data link connector
terminal
"2". This data is transmitted at a high frequecy
which requires a
"Scan tool" for interpretation. There
are several
"Scan tools" available for reading this
information.
With an understanding
of the data which the tool
displays, and knowledge of the circuits involved, the
tool can be
very useful in obtaining information which
would be more difficult or impossible to obtain with
other equipment.
"Scan tools" do not make the use of diagnostic charts
unnecessary, nor
can they indicate exactly where a
problem is in a particular circuit. Trouble Tree
Charts
incorporate diagnosis procedures using a "Scan tool"
where possible and most charts require the use of a
"Scan tool" when it is applicable.
A "SCAN TOOL" THAT DISPLAYS FAUL TV
DATA SHOULD NOT BE USED AND THE
PROBLEM SHOULD BE REPORTED TO THE
MANUFACTURER. THE USE OF A FAUL TV
"SCAN TOOL" CAN RESULT IN MIS­
DIAGNOSIS
AND UNNECESSARY PARTS
REPLACEMENT.
ECM's have two (2) modes for transmitting
information. The
following information will describe
the system operation in each
of the modes.
Data List (FO)
On engines that can be monitored in the "Open"
mode, certain parameters can be observed
without changing the engine operating
characteristics. The parameters capable
of being
read vary with engine families.
Most "Scan tools"
are programmed so that the system will go
directly into the data link connector mode
if the
"Open" mode is not available.
''SCAN TOOL'' LIMITATIONS AND USE
The "Scan tool" allows a quick check of sensors
and switches which are inputs
to the ECM. The
"Scan tool" allows one to manipulate wiring
harnesses or components under the hood while
observing the "Scan Tool" readout. This helps in
locating intermittents
with the engine not
running.
INTERMITTENT CONDITIONS
The "Scan tool" is helpful in cases of intermittent
operation. The
tool can be plugged in and
observed while driving the vehicle under the
condition
where the light comes "ON" momen- tarily,
or the
engine driveability is poor
momentarily.
If the problem seems to be related
to certain areas
that can be checked on the "Scan ~
tool", then those are the positions that should be
checked while driving the vehicle. If there does
not seem to
be any correlation between the
problem and any specific circuit, the
"Scan tool"
can be checked on each position, watching for a
period
of time to see if there is any change in the
readings that indicates intermittent operation.
The
"Scan tool" is also a useful and quick way of
comparing operating parameters of a poorly
operating engine with a known good one. For
example; A sensor may shift in
value but not set a
diagnostic trouble code. Comparing with a known
good vehicle may uncover the problem.
The
"Scan tool" has the ability to save time in
diagnosis and prevent the replacement
of good
parts. The key to using the
"Scan tool" success­
fully
for diagnosis lies in the technicians ability to
understand the system he is trying to diagnose as
well as an understanding of the "Scan tool's"
limitations. Therefore, the technician should read
the tool operating manual to become familiar
with
the tool. The following information will describe
most of the "Scan tool" positions and how they
can be helpful in diagnosis.
"SCAN TOOL" POSITIONS
INJECTOR PULSE WIDTH
In this position, the reading is given in milli­
seconds which is the on time that the ECM is
commanding to the injector(s).
CLOSED LOOP/OPEN LOOP
This position will indicate whether the engine
control system
is operating in open or closed
loop. Most systems go closed loop after a certain
amount of run time, when engine coolant
temperature
is high enough, and the oxygen
sensor becomes active.
TROUBLE CODES
Will display any trouble codes stored in the ECM
memory.
THROTTLE POSITION (TP) SENSOR
Values read will be the voltage as seen by the ~
ECM. The voltage should be the TP sensor
specification
with the throttle closed and go up to
about 5 volts with
wide open throttle.
•

6E2-18 DRIVEABILITV AND EMISSIONS
TOOLS NEEDED TO SERVICE THE SVSJEM
The system requires a data link connector read-out (Scan) tool, tachometer, test light, ohmmeter, digital voltmeter
with 10 megohms impedance (J-39200), vacuum gage and jumper wires for diagnosis. A test light or voltmeter
must be used when specified in the procedures. They must NOT be interchanged. For more complete information
on the operation
of these tools, see the manufacturer's instructions.
Voltmeter
Voltage position measures amount of voltage when
connected in
parallel to an existing circuit. A digital
voltmeter
with 10 megohm input impedance is used
because this type
of meter will not load down the
circuit and
result in faulty readings. Some circuits
require accurate
low voltage readings, and some
circuits in the engine
control module have a very high
resistance.
Digital multimeter: J-39200 or equivalent
Fig. 6E2-4
Ammeter
When used as ammeter, this meter also accurately
measures extremely low current flow. Refer to meter
instructions
for more information.
• Selector must be set properly for both function
and range.
DC is used for most automotive
measurements.
Digital multimeter: J-39200 or equivalent
Ohmmeter
Measures resistance of circuit directly in ohms.
Refer to meter instructions
for more information.
• OL Display in all ranges indicates open circuit.
• Zero display in all ranges indicates a short circuit.
• Intermittent connection in circuit may be
indicated by digital reading that will not stabilize
on circuit.
• Range Switch
200 -Reads ohms
directly
2K, 20K, 200K -Reads ohms in thousands
2M and 20M -Reads ohms in
millions
Digital multimeter:
J-39200 or equivalent
Vacuum pump (20 in. hydragyrum minimum)
Use gage to monitor manifold engine vacuum and the
hand pump to check vacuum sensors,
solenoids and
valves.
Vacuum pump: J-23738
Fig. 6E2-5
Unpowered test light
Used to check wiring for complete circuit and short to
ground
or voltage.
Unpowered test light: J-34142-A
Fig. 6E2-6
•

6E2-26 DRIVEABILITV AND EMISSIONS
ENGINE CONTROL MODULE WIRING DIAGRAM (1) (SOHC}
To ignition
switch 10 A
Meter fuse Underhood
connectors
located driver's side
shock tower
"Check Engine" MALFUNCTION
.-----------..:.:.1 N.:.:D:..:.IC=A~T~O:..:.R.:....=:.LA..::.M.:..::P:..___-,--___.:O:..:.R.:.:.N::.._IY.....:E:..:L=----1 c4
.------~~----~~O:..:R:..:N/~8~L=-=K--~ C 2
TCM
(C91-C8)
Engine Control Module(ECM)
"Check
engine" light control
DLC Diagnostic Request Input
Serial
data inpuVoutput
.--------f---+-....::...::;_;__=---_-1 A 12 System ground
Common
Data Link Connector (White) Chamber L.....::.=::....=..:=-=----+---1 C12 System ground
Intake air
temperature sensor
Throttle position
sensor
Manifold absolute pressure sensor
Engine
Coolant Temperature sensor Heated
oxygen
J-,.:..:W:.:..H.:..:T.:.:I8:..:L:.:U:......__ __ ....-To Fuel
RED/BLU (M/T)
1---=-'L T'-.!8~L:!:U'--l(.::::A/T!....!...!....) ---< f------lt+-~!,!..._'H---1 83
BRN/8LK
84
8RN/WHT 85
BRN/RED 87
8RN!YEL
BS
1---------~~~B~L~U~/8~L~K~--I 07
BLK/WHT
TCM
(C91-C6)
BLK/WHT 1------------4>---< t-----=~:..:.:..:_.:..:_ ....... -1 02
1-----------~ f----'-=-'-==--....-1 06
1-----------~ f--.-::..:=.=.:....=..c~-+--1 A 1
BLU/ORN
H02S Signal Input
H02S Ground
lAC coil "A" HI
lAC coil "A" LO
lAC coil "B" HI
lAC coil "B" LO
IAC=IDLE AIR CONTROL
Intake
Air Temperature(IAT)
signal input
Sensor ground
TPS signal input
5 volt reference
MAP
signal input
1---------'----...._.G:=.:..:.RY-=--------1 A 11 Sensor ground
1-------;---.:::G:..:R_;_YI:...::8:..:L::..:K:__---I 012 Engine Coolant Temperature
signal input
Fig. 6E2-17
•

DRIVEABILITY AND EMISSIONS 6E2-29
ENGINE CONTROL MODULE WIRING DIAGRAM (1) (DOHC)
Underhood connectors
located driver's side
shock
tower
To ignition
switch 7.5AMP ,.... ~ ®
I
I
Meter fuse I "Check Engine" I Malfunction I Indicator Lamp I
I
'
I 8LK/8LU I
D
I l TCM (C91-C8) 1
~ 1 2 ~ ~ co.;;mo~~ : ata Link Connector (White) Chamber 1 0 Common1 Chamber 1 Heated oxygen -= I
rg
=F
leair s ontrol C] alve
ld c v
M
te anifold
air
mperature sensor
Throttle position sensor
Manifold absolute pressure sensor
Engine
Coolant
T emperature
Sensor
sensor I
I
-A/IN-1:'1 WHT/8LU I
~ RED/8LU (M/TI I
~ ""21 L T 8LU (A/TI II ....::....1 ,1,
8LK/GRN :,
I
I
I
I
cam l:
I
I
Au A )I y"-\1 r--
8 8LK/WHT I I
I
I
I
8 ~ 1--II
~ r£ \ 'I A ,1,
8LU/ORN I
r£ ~ I
8 ~ f--I A I
I
I
_A& a A I y"-I r--I 8 I
I
I
Fig. 6E2-20
VLT
ORNNEL
ORN/8LK
8LK/8LU
I 8LK/8LU
To Fuel
pump relay
( ) RED ( v v
8LU
~ -8RN/8LK
8RN/WHT
8RN/RED
8RNNEL
8LU/8LK
TCM (C91-C6)
8LK/WHT !
RED/8LU
8LU/ORN
TCtM
(C91-C5)
GRY/RED
GRY
GRY/8LK Engine
Control
Module (ECMI
.-----
AS "Check engine" light control
C4 DLC Diagnostic Request lnpu
C2 Serial data input/output
A12 System ground
C12 System ground
83
H02S Signal input
82 H02S ground
84
lAC coil "A" HI
85 lAC coil "A" LO
87 lAC coil "8" HI
86 lAC coil "8" LO
lAC = Idle Air Control
D7 MAT signal input
D2 Sensor ground
D6 TPS signal input
A1 5 volt reference
D9 MAP signal input
A11 Sensor ground
D12 Engine Coolant Temperatur e signal input
......__

6E2-34 DRIVEABILITY AND EMISSIONS
''SCAN TOOL" ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK
The Diagnostic Circuit is an organized approach to identifying a problem created by an electronic engine control
system malfunction. It must be the starting point for any drive ability complaint diagnosis, because it directs the
service technician to the next
logical step in diagnosing the complaint.
The "Scan tool" data listed in the table may be used for comparison, after completing the on-board diagnostic
system check and finding the on-board diagnostics functioning
properly with no trouble codes displayed. The
"Typical Data Values" are an average of display values recorded from normally operating vehicles and are
intended
to represent what a normally functioning system would typically display.
A "SCAN tool" that displays faulty data should not be used, and the problem should be reported to the
manufacturer. The use of a faulty "SCAN tool" can result in misdiagnosis and unnecessary parts
replacement.
Only the parameters listed below are used in this manual for diagnosis. If a "Scan tool" reads other parameters,
the
values are not recommended for use in diagnosis. For more description on the values and use of the "Scan
tool" to diagnosis engine control module inputs, refer to the applicable component diagnosis section in
"Component System", Section "6E2-C". If all values are within the range illustrated, refer to "Symptoms", Section
"6E2-B".
"SCAN TOOL" DATA
Test under following condition.
Idle I Upper radiator hose hot I Closed throttle I Park or neutral I "Closed Loop" I All Accessories "OFF"
"SCAN TOOL" position Units displayed Typical data value
Engine Speed RPM ± 50 RPM from desired RPM in drive (A/T) ± 100 RPM from desired rpm in neutral (MIT)
Desired
RPM RPM Engine control module idle command (varies with Engine load and temperature)
ENG COOL TEMP
Degrees Celsius/Fahrenheit 85-105 (185-221)
Intake Air Temperature (IAT) Degrees Celsius/Fahrenheit 10-90 (50-199) (varies with Underhood
temperature and sensor location)
Manifold Absolute Pressure Volts 1 - 2 (varies with manifold and barometric pressure)
Barometric Pressure Volts Varies depending on altitude
Throttle Position Volts .50-1.25
Throttle Angle 0-100% 0 at Idle
BPW (base pulse width) Milliseconds 0.0 to 499.9
Oxygen Sensor Volts Volts .1 - 1 (varies continuously)
S.T. Fuel
Trim Counts 108-154
LT. Fuel Trim Counts 116-145
Loop Status
Open/Closed "Closed Loop"
Fuel Trim Cell 0/1 1
Spark Advance Degrees Varies continuously
Ignition Control Enable No/Yes Yes
Knock Retard
Degrees
0-45
Shift Light OFF/ON OFF
Idle Air Control
Counts (steps) 1 -50 depending on engine load
PARK/NEUTRAL P-N and R-D-L Park/Neutral (AUTO)
A/C Request Switch Yes/No No
A/C Request ON/OFF "OFF"
Vehicle Speed
Mile per hour/KPH 0
Power Steering
NORMAL/HI PRESSURE NORMAL
EGR Solenoid
ON/OFF OFF
AIR Control Solenoid
ON/OFF OFF
Induction Air Solenoid OFF/ON OFF ("ON" above 5000 RPM)
Air Fuel Ratio Ratio 0-25.5:1
EVAP Purge OFF/ON OFF
Idle Throttle No/Yes Yes
Fuel Trim Enable No/Yes Yes
System Voltage Volts 13-15
PROM ID 000 0-65535
Time From Start 00:00