open hood ISUZU TROOPER 1995 User Guide

3F4-16 SUPPLEMENTAL RESTRAINT SYSTEM (SRS) STEERING WHEEL & COLUMN
Alignment mark
Fig. 3F4-38
\fCAUTION:
When turning the SRS coil clockwise to full, stop
turning if resistance is felt. Forced furtherturning
may damage to the cable in the SRS coil.
6. Steering column cover
• When installing the steering column cover, be
sure
to wire (through each harness) as
illustrated so that the harnesses starter
switch,
combination switch and SRS coil may
not catch wiring (Fig. 3F4-39).
Starter switch
harness
Combination switch harness
Inflator module harness
5. Steering wheel
Fig. 3F4-39
• Align the setting marks made when re­
moving.
WCAUTION:
Never apply force to the steering wheel in
direction
ofthe shaft by using a hammer or other
impacttools in an attempt to remove the steering
wheel. The steering
shaft is designed as an
energy absorbing unit.
• Tighten the steering wheel fixing nut to the
specified torque. Torque
N·m (lb·ftl 34
(25)
4. Inflator module
• Support the module and carefully connect the
module connector.
NOTE:
Pass the lead wire through the tabs on the plastic
cover (wire protector) of inflator to prevent lead
wire from being pinched.
• Secure the module with one bolt to relieve
weight on the connector wire.
• Tighten bolts to specified sequence as figure
(Fig. 3F4-40).
Torque
N·m (lb-in) 8 (69)
Fig. 3F4-40
3. Driver knee bolster (reinforcement)
2. Steering lower cover
• Install the engine hood opening lever.
1. Front console assembly
• Connect the wiring harness connectors.
• Install the transmission (for M/T) and transfer
control lever knob.
• Connect the yellow 3way SRS connector located
under the steering column.
• Connect the battery "-"terminal cable.
SYSTEM INSPECTION
• Set ignition to "ON" while watching warning
light.
• Light should flash 7 times and then go off. If
lamp does not operate correctly, refer to
Section 9J.
•

6E2-2 DRIVEABILITY AND EMISSIONS
DRIVEABILITV AND EMISSIONS GENERAL INFORMATION
CONTENTS
General Information
Driveability ....................... .
Emissions
........................ .
Maintenance
Schedule .............. .
Introduction ...................... .
Electronic Engine
Control .......... .
What This Section Contains ........ .
Blocking Drive Wheels
Visual/Physical
Underhood Inspection
6E2-3
6E2-3
6E2-3
6E2-3
6E2-3
6E2-3
6E2-3
6E2-3
Basic
Knowledge required . . . . . . . . . . . . 6E2-4
Basic Electric Circuits . . . . . . . . . . . . . .
6E2-4
Use
of Circuit Testing Tools . . . . . . . . . 6E2-4
Use
of Digital Volt-Ohm Meter (DVOM). 6E2-4
Diagnostic
Information . . . . . . . . . . . . . . . 6E2-4
"Check Engine" Malfunction Indicator
Lamp (MIL) . . . . . . . . . . . . . . . . . . . . 6E2-4
Intermittent "Check Engine"
Malfunction Indicator Lamp (MIL) . . 6E2-4
Reading Diagnostic
Trouble Codes . . . 6E2-5
Clearing
Trouble Codes . . . . . . . . . . . . 6E2-5
Diagnostic Test
Mode .............. 6E2-5
Engine Control
Module Learning
Ability . . . . . . . . . . . . . . . . . . . . . . . . 6E2-6
Field
Service Mode . . . . . . . . . . . . . . . . 6E2-6
Standard Nomenclature
for Certain
Electrical/Electronic
Components
and Systems . . . . . . . . . . . . . . . . . . . 6E2-6
Abbreviations and Glossary of Terms ..... 6E2-11
Driveability and Emissions
Section Summary ................... 6E2-12
Section .,. A"
Diagnostic Procedure Summary ...... 6E2-13
Data Link Connector
"SCAN Tools" ..... 6E2-14
Data
List (FO) ...................... 6E2-14
"SCAN Tool" Limitations and Use ...... 6E2-14
Intermittent Conditions ............ 6E2-14
"SCAN Tool" Positions ............... 6E2-14
Injector Pulse Width ............... 6E2-14
Closed Loop/Open Loop . . . . . . . . . . . .
6E2-14
Trouble Codes ................... 6E2-14
Throttle Position (TP) Sensor . . . . . . . . 6E2-14
Throttle Angle . . . . . . . . . . . . . . . . . . . 6E2-15 Heated
Oxygen
Sensor (H02S)
Vehicle Speed Sensor (VSS) ....... .
Programmable Read Only Memory ID .
Revolution
Per Minute (RPM) ...... .
Mile Per Hour (MPH) ............. .
Engine
Coolant Temperature (ECT) .. .
Intake Air Temperature (IAT)
Sensor
...................... .
Manifold Absolute Pressure (MAP) .. .
Barometric Pressure (BARO) ....... .
Exhaust Gas Recirculation
(EGR)
(ON/OFF) .................... .
Short Term (S.T.) Fuel Trim and
Long Term
(LT.) Fuel Trim ...... .
Long Term
(LT.) Fuel Trim ........ .
Idle Air Control (lAC) Counts ....... .
Desired Revolution
Per Minute ..... .
Air Conditioning (A/C) Request ..... .
Air Conditioning (A/C) Clutch ...... .
Power Steering Pressure (PSP)
Switch ...................... .
Battery Positive Voltage .......... .
Spark Advance .................. .
Start Up Engine Coolant .......... .
Engine
Speed (RPM) ............. .
Fuel Trim Enable ................ .
Air/Fuel Ratio .................. .
Induction Air Control ............. .
Section B -Driveability Symptoms ... .
Section C -Component Systems .... .
Engine
Control Module (ECM)
and
Sensors .................. .
Fuel Control System ............. .
Electric
Fuel Pump (in-tank) ....... .
Evaporative Emission
(EVAP)
Control System ................ .
Ignition Control (IC) .............. .
Exhaust Gas Recirculator
(EGR) .... .
Air Conditioning (A/C) Clutch Control .
Positive Crankcase Ventilation (PCV) .
Tools Needed
to Service the System .... .
General Specifications
............... .
Vacuum Hose Routing Diagram
........ .
6E2-15
6E2-15
6E2-15
6E2-15
6E2-15
6E2-15
6E2-15
6E2-15
6E2-15
6E2-15
6E2-15
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-16
6E2-17
6E2-17
6E2-17
6E2-17
6E2-17
6E2-17
6E2-17
6E2-17
6E2-18
6E2-21
6E2-22
~
... ...
•

DRIVEABILITY AND EMISSIONS 6E2-11
Former ISUZU Name New ISUZU Name Term
Throttle Position Switch Wide Open Throttle Switch -WOT Switch
Throttle Switch
Wide Open Throttle Switch -WOT Switch
Throttle Valve Throttle
Body -TB
TPS Throttle Position Sensor -TP Sensor
Transmission ECU Transmission Control Module -TCM
TWC Three
Way
Catalytic Converter -TWC
Vacuum Switching Valve Vacuum Switch Valve -VSV
Vehicle Speed Sensor Vehicle
Speed Sensor
-VSS
vss Vehicle Speed Sensor -VSS
vsv Vacuum Switch Valve -VSV
WOT
Wide Open Throttle -WOT
ABBREVIATIONS AND GLOSSARY OF TERMS
Abbreviations used in this section are listed below in
alphabetical order with an explanation of the
abbreviation. There are some variations in the use
of
periods and in capitalization (as mph, m.p.h., Mph, and
MPH) for abbreviations used in this Section, but all
types are acceptable.
A/T -AUTOMATIC TRANSMISSION
AVM-ANALOG VOLT METER
CKT -CIRCUIT
DOHC-DUAL OVERHEAD CAMSHAFTS
DTM-DIAGNOSTIC TEST MODE
A particular state of operation.
DVOM-DIGITAL VOLT OHM METER
ECT -ENGINE COOLANT TEMPERATURE
ECM-ENGINE CONTROL MODULE
A metal box (located in passenger compartment)
containing
electronic circuitry which electrically
controls
and monitors air/fuel and emission systems
on
computer command control, and turns "ON" the
"Check Engine"
Malfunction Indicator Lamp when a
malfunction occurs in the system.
EGR-EXHAUST GAS RECIRCULATION
Method of reducing NOx emission levels by causing
exhaust gas
to be added to air/fuel mixture in
combustion chamber, thus
cooling combustion.
FED-FEDERAL
Vehicle/Engine available in all states except California.
GROUND
The negative (-) side of the battery. Also could be a
wire (conductor) shorted to ground.
HC-HVDROCARBONS
One of the pollutants found in engine exhaust.
Hg-MERCURV
A calibration material used as a standard for vacuum
measurement.
HIGH IMPEDANCE VOLTMETER
Has high opposition to the flow of electrical current.
Good
for reading circuits with low currentflow, such as
found in electronic systems because it allows tests to
be made without affecting the circuit.
IAT -INTAKE AIR TEMPERATURE
Air temperature in the intake manifold.
IAT-INTAKE AIR TEMPERATURE SENSOR
Measures the underhood temperature.
IC-IGNITION CONTROL
ECM controlled spark timing
IDEAL MIXTURE
The air/fuel ratio which provides the best
performance,
while maintaining maximum conversion
of exhaust emissions. Typically it is 14.7:1.
IGN-IGNITION
INPUTS
Information from sources (such as Engine Coolant
Temperature Sensors, Oxygen Sensor, etc.) to the
ECM that indicate how the systems are performing.
INTERMITTENT
Occurs now and then; not continuously. In electrical
circuits, refers to occasional open, short, or ground.
liP-INSTRUMENT PANEL
ISC-IDLE SPEED CONTROL
ECM-controlled solenoid used to route vacuum to
control idle speed under various engine loads.
KM/H-KILOMETER PER HOUR
A metric unit measuring speed needed to travel
distance of one kilometer (1 000 meters) in one hour.

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.
•

THROTTLE ANGLE
Displays in percent the amount the throttle is
open.
HEATED OXYGEN SENSOR (H02S)
The reading will be read out in millivolts (mv) with
a range from 1 to 999 mv. If the reading is
consistently
below 350 (350 mv), the fuel system
is running
lean as seen by the Engine Control
Module
(ECM) and if the reading is consistently
above
550 (550 mv), the system is running rich.
VEHICLE SPEED SENSOR (VSS)
Displays vehicle speed, useful in checking
speedometer accuracy.
PROGRAMMABLE READ ONLY MEMORY
(PROM)
ID
In this position the last4 digits of the Mem-Cal part
number will be displayed.
REVOLUTION PER MINUTE (RPM)
Displays engine speed. Often useful if extra
reference pulses are suspected. A sudden high
revolution per minute indication while at a steady
throttle
would indicate electrical interference
(EMI) in the reference circuit. This interference is
usually caused by ECM wires too close to ignition
secondary wires
or an open electronic ignition
ground circuit.
MILE PER HOUR (MPH)
Displays vehicle speed. Useful in checking
speedometer accuracy.
ENGINE COOLANT TEMPERATURE (ECT)
Displays engine temperature in degress centi­
grade.
After engine is started the temperature
should rise steadily to about
85-95·c, then
stabilize
when the thermostat opens.
INTAKE AIR TEMPERATURE (IAT)
SENSOR
Displays temperature of the intake manifold air.
Should read close to ambient air temperature
when the engine is cold, and rise
as underhood
and engine temperature increases.
DRIVEABILITY AND EMISSIONS 6E2-15
MANIFOLD ABSOLUTE PRESSURE (MAP)
The Manifold Absolute Pressure (MAP) Sensor
produces a low signal voltage when MAP is low
(high vacuum) and a high voltage when the
pressure is high (low vacuum).
With the ignition on and the engine stopped, the
manifold absolute pressure is equal
to
atmospheric pressure and the signal voltage will
be high. This information is used by the ECM as an
indication of vehicle altitude and is referred to as
barometric pressure. Comparison of this
barometric pressure reading
with a known good
vehicle
with the same sensor is a good way to
check accuracy
of a "suspect" sensor. Readings
should be the same
±0.4 Volt.
MAP
Sensors have a colored plastic insert visible
in the connector cavity.
Sensors with the same
insert color are identical in calibration. The
harness electrical connector color should also be
the same
as the sensor insert color.
BAROMETRIC PRESSURE (BARO)
Displays the MAP reading before the engine was
started. This value
will vary depending on
Barometric Pressure and altitude.
EXHAUST GAS RECIRCULATION (EGR)
(ON/OFF)
The exhaust gas recirculation system uses a valve
controlled by vacuum to feed a small amount of
exhaust gas back into the intake manifold to
control formation
of NOx. Like all ECM outputs the
"Scan tool" only indicates that the ECM has
commanded the function and does
not indicate
that the function has
really happened.
SHORT TERM (S.T.) FUEL TRIM AND LONG
TERM (L.T.) FUEL TRIM
On Fuel Injected Engines, normal readings for
these positions are around 128. If higher, it
indicates that the ECM is adding fuel to the base
fuel calculation because the system is lean.
If the
numbers are below 128, the
ECM is taking out fuel
from the base calculation because the system is
rich. The
S.T. Fuel Trim is short term corrective
action while the
L.T. Fuel Trim portion (which is a
long term correction)
will only change if the
intergrator has seen a condition which lasts
for a
calibrated period
of time.

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

6E2-38 DRIVEABILITV AND EMISSIONS
CHART A-1
WILL NOT FLASH DIAGNOSTIC TROUBLE CODE (DTC) 12
NO "CHECK ENGINE" MALFUNCTION INDICATOR LAMP (MIL)
Circuit Description:
There should always be a steady "Check Engine" Malfunction Indicator Lamp (MIL), when the ignition is "ON" and
engine stopped. Battery positive
voltage is supplied directly to the light bulb. The Engine Control Module (ECM)
will control the light and turn it "ON" by providing a ground path through the VL T wire from the ECM to the bulb.
Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
CD The Test Light provides a ground source to the "Check Engine" MIL. If the circuit is okay the "Check Engine"
MIL should
be "ON" when the terminai"A5" is probed.
® Battery feed terminals "C16" and "B1" are protected by a 30 amp ECM fusible link in relay/fuse center under
the hood near the battery.
If terminals "C16" and "B1" have voltage, the ECM grounds or the ECM are faulty.
® Using a test light connected to 12 volts, probe each of the system ground circuits to be sure a good ground is
present. Refer to the
"ECM Terminal End View" in front of this section for ECM pin locations of ground
circuits.
Diagnostic Aids;
Engine runs OK, check;
• Faulty light bulb.
•
VL T wire open.
• Meter fuse blown. This will result in no oil or generator lights, seat belt reminder, etc.
Engine cranks, but
will not run.
• Continuous battery-fuse or fusible link open. • Ignition RED/GRN wire to ECM open.
• ECM ignition fuse open. • Poor connection to ECM.
• Battery RED/WHT wire to ECM open.
TO FUEL .._..,==~ ,__,__-----, PUMP 15A
RELAY .--------~~-RED/WHT Engine
Control
Module(ECM)
BATIERY VOLTAGE
INPUT
ECM FUSIBLE RED/WHT TO LINK 30A '\.. BATIERY ~ VOLTAGE---BLK!RED ~---.-RED/WHT
TO IGNITION - BLK!YEL ~~~-BLK!YEL --'--'~"'---..__
SWITCH TO EGR VALVE VSV
CANISTER PURGE VSV
SECONDARY INTAKE VSV
REED VALVE VSV TO KS MODULE
LOCATED
PASSENGER
SIDE FENDER CHASSIS GROUND
"CHECK ENGINE"
MALFUNCTION
I/P CONNECTOR INDICATOR LAMP
METER (BLUE)
("";:; TO - BLK!YEL ~(---VEL~(;-VLT IGNITION 7.5A SWITCH
BLK ~ GRN MAIN RELAY
SOCKETEND SPLICES
TO ECM TERM. "D1" ECM SYSTEM GROUND
DATA
LINK CONNECTOR(WHITE)
1/P CONNECTOR
(WHITE)
BA TIERY VOLTAGE INPUT
IGNITION
VOLTAGE INPUT
"CHECK ENGINE"
MALFUNCTION
INDICATOR
LAMP DRIVER
~
DIAGNOSTIC REQUEST INPUT
' VIEW Fig. 6E2-24
./ .................................... __________________________ _

DRIVEABILITV AND EMISSIONS 6E2-49
CHART A-5
FUEL PUMP RELAY CIRCUIT
• REMOVE FILL CAP. • IGNITION "ON", ENGINE STOPPED.
• LISTEN FOR PUMP TO RUN AT FILLER NECK. • PUMP SHOULD RUN FOR 2 SECONDS, THEN SHUT "OFF". DOES IT?
I
CD
$ $
• REMOVE RELAY FROM UNDERHOOD RELAY CENTER. INTERMITTENT PROBLEM. SEE I • WITH TEST LIGHT TO GROUND, PROBE RED/WHT "DIAGNOSTIC AIDS" ON FACING~. WIRE CAVITY OF FUEL PUMP RELAY CONNECTOR.
• LIGHT SHOULD BE "ON". IS IT?
I
$
$
• JUMPER RED/WHT WIRE AND BLK/RED WIRE WITH A OPEN IN RED/WHT WIRE CIRCUIT. I FUSED JUMPER. • LISTEN FOR FUEL PUMP TO RUN. DOES IT?
I
$ $
• IGNITION "OFF" FOR 10 SECONDS. • JUMPER WIRE STILL IN PLACE. ® • CONNECT TEST LIGHT BETWEEN BLK WIRE AND • PROBE FUEL PUMP CONNECTOR AT FUEL
PNK/WHT WIRE OF FUEL PUMP RELAY CONNECTOR. TANK WITH TEST LIGHT TO GROUND. • IGNITION "ON", LIGHT SHOULD BE "ON" FOR 2 • LIGHT SHOULD BE "ON". SECONDS, THEN SHUT "OFF". IS IT? IS IT?
I
$
$ ~ $
• IGNITION "OFF" FOR 10 SECONDS. I FAULTY RELAY I OPEN IN GROUND TO I OPEN IN BLK/RED WIRE I • BACK PROBE TERMINAL "C3" OF FUEL PUMP ENGINE CONTROL MODULE (ECM) OR WITH TEST LIGHT TO GROUND. FAULTY FUEL PUMP • IGNITION "ON". • LIGHT SHOULD BE "ON" FOR 2 SECONDS.
IS IT?
I
$ $
OPEN IN PNK/WHT WIRE FAULTY ENGINE OR CONTROL MODULE
OPEN IN BLK WIRE (ECM)

6E2-1 04 DRIVEABILITV AND EMISSIONS
Engine Coolant Temperature (ECT) Sensor
A "Scan tool" displays engine temperature in degrees
centigrade. After engine is started, the temperature
should rise steadily to about 90°C then stabilize when
thermostat opens. If the engine has not been run for
several hours (overnight), the engine coolant
temperature (ECT) and intake air temperature (IAT)
readings should be close to each other. A fault in the
ECT sensor circuit should set a diagnostic trouble code
(DTC) 14. The DTC charts also contain a chart to check
for sensor resistance values relative to temperature.
Intake Air Temperature (IAT) Sensor
A "Scan tool" displays temperature of the air entering
the engine and
should read close to ambient air
temperature when engine
is cold, and rise as under
hood temperature increases.
If the engine has not
been run for several hours (overnight), the IAT sensor
temperature and
ECT readings should be close to each
other. A
failure in the IAT sensor circuit should set a
DTC 23. The DTC charts also contain a chart to check
for sensor resistance values relative to temperature.
Heated Oxygen Sensor (H02S)
The "Scan tool" has several positions that will indicate
the state
of the exhaust gases, Oxygen voltage,
integrator, and block learn. See "Scan tool" position
information in
"Introduction", "Driveability and
Emission," in this section.
A
problem in the oxygen sensor circuit, or fuel system,
should set a DTC 13 (open circuit), DTC 44 (lean
indication)/DTC 45 (rich indication). Refer to
applicable chart, if any of these DTC(s) were stored in
memory.
Throttle Position (TP) Sensor
A "Scan tool" displays throttle position in volts. On 3.2L
engine, Throttle position
(TP) sensor voltage should
read below 0.85 volts, with throttle closed and ignition
"ON", or at idle. Voltage should increase at a steady
rate
as throttle is moved toward wide open throttle.
The Engine
Control Module (ECM) has the ability to
auto-zero the TP sensor voltage if it is below about 0.85
volts. This means that any voltage less than 0.85 volts
will
be determined by the ECM to be 0% throttle.
Some
"Scan tools" have the ability to read the throttle
angle and should read 0%, when the throttle is closed.
A failure in the TP sensor or circuit should set a DTC 21.
Manifold Absolute Pressure (MAP) Sensor
"Scan tool" displays manifold pressure in volts. Low
pressure (high vacuum) reads a
low voltage, while a
high pressure
(low vacuum) reads a high voltage. A
failure in the Manifold Absolute Pressure (MAP) sensor
circuit
should set a DTC 33 and using the chart will find
the cause
of the problem. A DTC 33 may be set if a
rough or unstable
idle exists. CHART C-1 D can also be
used
to check MAP sensor.
Vehicle Speed Sensor (VSS)
A "Scan tool" reading should closely match with
speedometer reading with drive wheels turning. A
failure in the vehicle speed sensor circuit should set a
DTC 24.
AIR CONDITIONING (A/C) Request Signal
When air conditioning in "ON", the "Scan tool" should
indicate air conditioning "ON".
See
"Air Conditioning Compressor Clutch Control
System",
Section "6E2-C1 0" for A/C electrical system
diagnosis.
Power Steering Pressure (PSP) Switch
A "Scan tool" should read "OFF" normally, and "ON"
with high pressure. This reading may vary with
different "Scan tools". Refer to CHART C-1 E for power
steering pressure switch diagnosis.
Crankshaft Position (CKP) Reference Signal
The ignition control module sends a signal to the ECM,
which is used to calculate proper spark advance and
fuel delivery. A "Scan tool" will read this signal and is
displayed in revolution per minute.
See "Electronic
Ignition System",
Section "6E2-C-4" for more
information on the ignition system (ignition control).
Park/Neutral Position (PNP) Switch
A "Scan tool" should read park/neutral position when
in park, or neutral, and R-D, L, when in drive or
overdrive. This reading may vary with different makes
of tools. Refer to CHART C-1 A for park/neutral position
switch diagnosis.
Knock Sensor (KS)
A "Scan tool" will indicate when the knock sensor
module signals the ECM that knock is present. See
"Knock
Sensor System," Section "6E2-C5" for further
information on the knock sensor system.
ON-VEHICLE SERVICE
ENGINE CONTROL MODULE (ECM)
The ECM is programmed from the factory and has no replaceable calibration chip.
•

6E2-1 08 DRIVEABILITV AND EMISSIONS
CHART C-1A
PARK/NEUTRAL POSITION (PNP} SWITCH DIAGNOSIS
(AUTO TRANSMISSION ONL
V}
Circuit Description:
The
Park/Neutral Position (PNP) switch contacts are a part of the Mode switch assembly. They are closed to
ground in park or neutral and open in drive ranges.
The Engine
Control Module (ECM) supplies voltage through a current limiting resistor to BLU/PNK wire and
senses a
closed switch when the voltage on BLU/PNK wire drops to less than one volt.
The ECM uses the PNP signal as one ofthe inputs to control idle air, vehicle speed sensor diagnostics, and exhaust
gas recirculation.
If BLU/PNK wire indicates PNP (grounded), while in drive range, the ECM would be inoperative, resulting in
possible detonation.
If BLU/PNK wire indicates drive (open), a dip in the idle may exist when the gear selector is moved into drive range.
Test Description:
Number(s)
below refer to circled number(s) on the diagnostic chart.
1. Checks for a closed switch to ground in park position. Different makes of "Scan tools" will read PNP differently.
Refer to tool operator's manual for type of display used for a specific tool.
2 To gain access to the wiring for the Diode, it will be necessary to remove the lower cover of the underhood
fuse/Relay center.
MODE SWITCH PART OF
INHIBITOR SWITCH TRANSMISSION ASSEMBLY CONNECTOR
_[ BLK +~•+1-------rt--BLU/BLK -{~ PNK/BLU
-BLU/BLK
l
TO STARTER
RELAY COIL
SIDE OF RELAY
DIODE E-1
ENGINE CONTROL MODULE(ECM)
~ BLU/PNK ~ P/N POSITION SIGNAL
LOCATED IN
UNDERHOOD
FUSE/RELAY
CENTER
Fig. 6E2-61
Ill