service ISUZU TROOPER 1995 Workshop Manual

6E2-84 DRIVEABILITY AND EMISSIONS
DIAGNOSTIC TROUBLE CODE (DTC) 44
HEATED OXYGEN SENSOR (H02S) CIRCUIT
(LEAN HEATED OXYGEN SENSOR (H02S) SIGNAL INDICATED)
Circuit Description:
The engine control module supplies a voltage of about .43 volt between terminals "83" and "82". (If measured
with a
10 megohm digital voltmeter, this may read as low as .32 volts.) The Heated Oxygen Sensor (H02S) varies
the
voltage within a range of about 1 volt, if the exhaust is rich, down through about .1 0 volt, if exhaust is lean.
The sensor is like an open circuit and produces no voltage, when it is below about 360°C (600°F). An open sensor
circuit,
or cold sensor, cause "Open Loop" operation.
Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
CD Diagnostic Trouble Code (DTC) 44 is set, when the 02S signal voltage is fixed below .1 00 mV and the
following:
• Throttle
position sensor greater than 9.8%.
• No DTC 21 or 33. • Oxygen signal voltage is steady between .347
volt and .547 volt.
•
The engine has been running at least for 180 •
seconds. • • System is operating in "Closed Loop". •
Engine Operation Temperature 69SC (155°F).
All of the above conditions present for 25 sec .
Integrator not at 128 .
Diagnostic Aids:
Using the "Scan tool", observe the block learn value at different revolution per minute. The "Scan tool" also
displays
the block cells, so the block learn values can be checked in each ofthe cells, to determine when the DTC 44
may have been set.
If the conditions for DTC 44 exist, the block learn values will be around 150.
•
Check for ground in wire between connector sensor.
• Fuel Contamination-Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the
injector. The water causes a
lean H02S signal and can set a DTC 44.
• Fuel Pressure-System will be lean if pressure is too low. If may be necessary to monitor fuel pressure,
while driving the car at various road speeds and/or loads to confirm. See Fuel System diagnosis CHART A-5.
• Exhaust Leaks -lfthere is an exhaust leak, the engine can cause outside air to be pulled into the exhaust and
past the sensor.
Vacuum or crankcase leaks can cause a lean condition.
• If DTC 44 is intermittent, refer to Section "6E2-8".
• Fuel
Injectors-The wrong fuel injector(s) could be the cause of a lean H02S signal condition. Verify that the
correct
fuel injector(s) are installed in the vehicle. Refer to the service parts manual for correct part and part
number.
Refer
to "Engine Control Module and Sensors", Section "6E2-C1" for proper diagnosis.
TRANSMISSION
HARNESS
CONNECTOR
~BLK1
TRANSMISSION
HARNESS CONNECTOR
(BLUE) I /' BL~GRN~r-~----------~-------BLU
RED/BLU (MfT) --(( 1
1 ; « RED
(BLUE) ~
PASSENGER Q SIDE
LT BLU (A/T) L
WHT/RED 1
P:::l=t=t1 l BL~GRN ----.-----BL~GRN
BLK!YEL BL~BLU FENDER 02 --·S HEATER ELEMENT l
ENGINE
DRIVER'S SIDE BLOCK REAR AT CYLINDER
TRANSMISSION HARNESS _ HEAD CONNECTOR (BLUE)
10A -----BL~GRN ____ .,.... ~3EL PUMP RELAY
Fig. 6E2-47
ENGINE CONTROL
MODULE(ECM)
H02SGROUND REFERENCE
H02SSIGNAL
ECM GROUNDS
ECM GROUNDS
..

6E2-90 DRIVEABILITY AND EMISSIONS
INTERMITTENTS
Definition: Problem may or may not turn "ON" the
"Check Engine" malfunction indicator lamp or store
Diagnostic
Trouble Code (DTC).
DO NOT use the DTC charts in "Engine Components/
Wiring Diagrams/Diagnostic
Charts," Section "6E2-A"
for intermittent problem. The fault must be present to
locate the problem. If a fault is intermittent, use of DTC
charts may result in replacement of good parts.
•
• Most intermittent problems are caused by faulty
electrical
connections or wiring. Perform careful
visual/physical
check as described at start of
"Symptoms," Section "6E2-B." Check for:
Poor mating
of the connector halves. or
terminal not fully seated in the connector body
(backed out).
Improperly formed or damaged terminal. All
connector
terminals in the problem circuit
should be carefully reformed or replaced to
insure proper contact tension.
Poor
terminal to wire connection. This
requires removing the
terminal from the
connector body to check. Refer to
SECTION 8
"Wiring Harness Service,"
If a visual/physical check does not find the cause
of the problem, the car can be driven with a
voltmeter connected to a suspected circuit. A
"Scan tool" can also be used to help detect
intermittent conditions. An abnormal
voltage, or
"Scan" tool reading, when the problem occurs,
indicates the
problem may be in that circuit. If the wiring
and connectors check
OK, and a DTC was
stored
for a circuit having a sensor, except for
DTC(s) 44 and 45, substitute a known good sensor
and recheck.
• Loss of DTC memory. To check, disconnect
throttle position (TP) sensor and idle engine until
"Check
Engine" malfunction indicator lamp comes
"ON". DTC 21 should be stored, and kept in
memory when ignition is turned "OFF". If not, the
Engine
Control Module (ECM) is faulty.
•
An intermittent "Check Engine" malfunction
indicator
lamp with no stored DTC may be caused
by:
Ignition coil shorted to ground and arcing at
spark
plug wires or plugs.
"Check
Engine" malfunction indicator lamp
wire to ECM shorted to ground.
Diagnostic
"test" terminal wire to ECM,
shorted to ground.
ECM grounds, refer to ECM wiring diagrams.
• Check for an electrical system interference caused
by a defective
relay, ECM driven solenoid, or
switch. They can cause a sharp electrical surge.
Normally, the problem will occur when the faulty
component is operated.
• Check for improper installation of electrical
options such as lights, 2 way radios, etc.
• Ignition control wires should be routed away from
spark plug wires, electronic ignition (EI) wires, El
housing, coil and generator. Ground wire from
ECM to El should have a good connection.
• If problem has not been found, refer to "ECM
Connector Symptom" charts at the end of
"Symptoms," Section "6E2-B."
HARD START
Definition: Engine cranks OK, but does not start for a
long time. Does eventually run, or may
start
but immediately dies.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
described at start of "Symptoms," Section "6E2-
B".
•
Make sure the driver is using the correct starting
procedure.
SENSORS
• CHECK: Engine coolant temperature sensor using
a
"Scan tool", compare engine coolant
temperature with ambient temperature
on
cold engine. -
If engine coolant temperature
readings
is 5 degrees greater than or less than
ambient air temperature on a
cold
engine, check resistance in engine
coolant temperature sensor circuit
or
sensor itself. Compare engine coolant
temperature sensor resistance value
to the "Diagnostic Aids" chart on
DTC
14 chart.
• CHECK: Manifold absolute pressure sensor.
Check for flooding and/or correct sensor
for vehicle.
• CHECK: TP sensor for binding or a high TP sensor
voltage with the throttle closed (should
read between 0.54 volt and 1.25 volts.)

FUEL SYSTEM
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
Fuel pump relay operation-pump should
turn "ON" for 2 seconds when ignition is
turned
"ON". Use CHART A-5.
Fuel injectors are correct for the vehicle.
Fuel
pressure, use CHART A-7.
Contaminated
fuel.
Engine fuse (visual inspect).
A
faulty in-tank fuel pump check valve will
allow
the fuel in the lines to drain back to
the tank after engine is stopped. To check
for this condition, perform fuel system
diagnosis CHART A-7.
IGNITION SYSTEM
• CHECK: For proper ignition voltage output with
spark tester J26792 or equivalent (ST-
125).
DRIVEABILITY AND EMISSIONS 6E2-91
• CHECK: Spark plugs. Remove spark plugs, check
for wet plugs, cracks, wear, improper
gap, burned electrodes, or heavy
deposits. Repair
or replace as necessary.
• CHECK: Bare or shorted wires.
• CHECK: Loose ignition coil ground.
ADDITIONAL CHECKS
• CHECK: Idle air control operation-use CHART C-
2C.
• CHECK: Basic engine problem. Refer to ENGINE
MECHANICAL DIAGNOSIS (SECTION
6A).
• CHECK: Service Bulletins for calibration updates.
SURGES AND/OR CHUGGLES
Definition: Engine power variation under steady
throttle or cruise. Feels like the car speeds
up and
slows down with no change in the
acceleration pedal.
PRELIMINARY CHECKS
• Perform the careful visual checks as described at
start
of "Symptoms," Section "6E2-B."
•
Be sure driver understands transmission
operation, and air conditioning compressor
operation
as explained in the owner's manual.
SENSORS
• CHECK: Heated oxygen sensor (H02S). The
H02S should respond quickly to different
throttle position, if it does not, check the
H02S for silicon or other contaminations
from fuel, or use of improper RTV sealant.
The sensor may have a white, powdery
coating and result in a high but false
signal voltage
(rich heated H02S signal
indication). The engine control module
will
then reduce the amount of fuel
delivered
to the engine, causing a severe
driveability problem. Also, watch for
green glycol contamination or cracking.
FUEL SYSTEM
• NOTICE: To determine ifthe condition is caused by
a rich
or lean system, the car should be
driven at the speed of the complaint.
Monitoring block learn will help identify a
problem.
Lean -Block learn above 142. Refer to
"Diagnostic Aids" on facing page of
diagnostic trouble code 44.
Rich -L.T. Fuel Trim above 118. Refer to
"Diagnostic Aids" on facing page of
diagnostic trouble code 45.
• CHECK: Fuel pressure while condition exists. Use
CHART A-7.
• CHECK: In-line fuel filter. Replace if dirty or
plugged.
IGNITION SYSTEM
• CHECK: For proper ignition voltage output using
spark tester (ST-125) J26792
or
equivalent .
• CHECK: Spark plugs. Remove spark plugs, check
for wet plugs, cracks, wear, improper
gap, burned electrodes, or heavy
deposits. Repair
or replace as necessary.
Also, check condition of electronic
ignition and spark plug wires.
• CHECK: Ignition timing. Using "Scan tool".
ADDITIONAL CHECKS
• CHECK: Engine control module grounds for being
clean, tight and in their proper location.
• CHECK: Vacuum lines for kinks or leaks.
• CHECK: Exhaust gas recirculation -There should
be no exhaust gas recirculation at idle.
Refer to CHART C-7.
• CHECK: Generator output voltage. Repair if less
than 9 or more than 16 volts.

DRIVEABILITV AND EMISSIONS 6E2-99
SECTION C
COMPONENTS SYSTEMS
CAUTION
When fasteners are removed, always reinstall them at the same location from which they were removed. If a
fastener needs
to be replaced, use the correct part number fastener for that application. If the correct part number
fastener is not available, a fastener of equal size and strength (or stronger) may be used. Fasteners that are not
reused, and those requiring thread locking compound will be called out. The correct torque value must be used
when installing fasteners that require it. If the above conditions are not followed, parts or system damage could
result.
Section
"C" provides information on the following:
• General description of components and sub-systems.
• On-vehicle service.
• Part names and group numbers.
• Diagnostic charts. These include a functional check of the system as well as diagnosis of any problem found in
the functional check.
For locations
of components, wiring diagrams, and engine control module terminal and view, refer to the front of
"Engine Components/Wiring Diagrams/Diagnostic Charts", Section "A".
Refer to the following sections for the appropriate sub-system information:
• C1 Engine Control Module (ECM) and Sensors ................................. Page 6E2-1 00
•
C2 Fuel Metering System .................................................. Page 6E2-116
• C3 Evaporative Emission (EVAP) Control System ............................... Page 6E2-134
• C4 Electronic Ignition (EI) System/Ignition Control (IC) ........................... Page 6E2-138
• C5 Knock Sensor (KS) System .............................................. Page 6E2-146
• C7 Exhaust Gas Recirculation (EGR) System ................................... Page 6E2-151
• C8 Shift Indicator Light (M/T Only) ........................................... Page 6E2-157
• C1 0 Air Conditioning (A/C) Compressor Clutch Control System ..................... Page 6E2-161
• C13 Positive Crankcase Ventilation (PCV) ....................................... Page 6E2-164
DIAGNOSTIC CHARTS
The following diagnostic charts can be found at the end of some of the sections.
• Chart C-1A Park/neutral Position (PNP) Switch Diagnosis (Auto Transmission only) .... Page 6E2-108
• Chart C-1 D Manifold Absolute Pressure (MAP) Output Check ...................... Page 6E2-11 0
•
Chart C-1 E Power Steering Pressure (PSP) Switch Diagnosis ...................... Page 6E2-112
• Chart C-1 F Heated Oxygen Sensor (H02S) Heater Check ......................... Page 6E2-114
• Chart C-2A Injector Balance Test ............................................. Page 6E2-128
• Chart C-2C Idle Air Control (lAC) System Check ................................. Page 6E2-130
• Chart C-2D Induction Air Control System Check (DOHC Only) ...................... Page 6E2-132
• Chart C-3 Evaporate Emission Canister Purge Valve Check ....................... Page 6E2-136
• Chart C-4D-1 Electronic Ignition (EI) Misfire at Idle ................................ Page 6E2-142
• Chart C-4D-2 Electronic Ignition (EI) Misfire Under Load ............................ Page 6E2-144
• Chart C-5 Knock Sensor (KS) System Check .................................. Page 6E2-148
• Chart C-7A Exhaust Gas Recirculation (EGR) System Check ....................... Page 6E2-154
• Chart C-8 Manual Transmission (MIT) Shift Light Check ......................... Page 6E2-158
• Chart C-1 0 Air Conditioning (A/C) System Functional Check ....................... Page 6E2-162

6E2-100 DRIVEABILITY AND EMISSIONS
SECTION C1
ENGINE CONTROL MODULE (ECM) & SENSORS
CONTENTS
General Description ...................... 6E2-1 00
Engine Control Module (ECM) .............. 6E2-100
Engine Control Module (ECM) Function ....... 6E2-1 00
Information Sensors ..................... 6E2-1 01
Engine Coolant Temperature (ECT) Sensor ... 6E2-101
Intake Air Temperature (IAT) Sensor ........ 6E2-101
Heated Oxygen Sensor (H02S) ........... 6E2-101
Throttle Position
(TP) Sensor ............. 6E2-102
Manifold Absolute Pressure (MAP) Sensor ... 6E2-102
Vehicle Speed Sensor (VSS) ............. 6E2-102
Knock Sensor (KS) (DOHC ONLY) .......... 6E2-102
Air Conditioning (A/C) Request Signal ...... 6E2-1 02
Power Steering Pressure (PSP) Switch ...... 6E2-1 02
Park/Neutral Position (PNP) Switch
(Auto only)
........................ 6E2-1 03 Diagnosis ............................. 6E2-1 03
Engine Control Module (ECM) .............. 6E2-1 03
Electrically Erasable Programmable Read
Only Memory ........................ 6E2-1 03
Engine Control Module (ECM) Inputs ....... 6E2-103
Engine Coolant Temperature (ECT) Sensor ... 6E2-1 04
Intake Air Temperature (IAT) Sensor ........ 6E2-1 04
Heated Oxygen Sensor
(H02S) ........... 6E2-1 04
Throttle Position
(TP) Sensor ............. 6E2-1 04
Manifold Absolute Pressure (MAP) Sensor
... 6E2-1 04
Vehicle Speed Sensor (VSS) ............. 6E2-1 04
Air Conditioning (A/C) Request Signal
Power Steering Pressure
(PSP) Switch ..... .
Crankshaft Position
(CKP) Reference Signal ..
Park/Neutral Position (PNP) Switch ....... .
Knock Sensor
(KS) ................... .
On-Vehicle Service ..................... .
Engine Control Module
(ECM) ............ .
Engine Control Module
(ECM) Replacement ..
Engine Coolant Temperature (ECT) Sensor ... .
Intake Air Temperature (IAT) Sensor ........ .
Heated Oxygen Sensor
(H02S) ............ .
Throttle Position
(TP) Sensor ............. .
Manifold Absolute Pressure (MAP) Sensor
.... .
Vehicle Speed Sensor
(VSS) ............. .
Power Steering Pressure
(PSP) Switch ...... .
Park/Neutral Position
(PNP) Switch ......... .
Chart C-1A Park/Neutral Position
(PNP)
Switch Diagnosis .................... .
Chart
C-1 D Manifold Absolute Pressure (MAP)
Output Check
...................... .
Chart
C-1 E Power Steering Pressure (PSP)
Switch Diagnosis .................... .
Chart
C-1 F Heated Oxygen Sensor (H02S)
Heater Check ....................... .
6E2-104
6E2-104
6E2-104
6E2-104
6E2-104
6E2-104
6E2-104
6E2-105
6E2-105
6E2-106
6E2-106
6E2-107
6E2-107
6E2-107
6E2-107
6E2-107
6E2-108
6E2-110
6E2-112
6E2-114
GENERAL DESCRIPTION
ENGINE CONTROL MODULE (ECM)
The Engine Control Module (ECM) (Fig. 6E2-50),
located under the instrument panel, is the control
center of the fuel injection system. If constantly looks
at the information from various sensors, and controls
the systems that affect vehicle performance. The ECM
also performs the diagnostic function of the system. It
can recognize operational problems, alert the driver
through the "Check Engine" malfunction indicator
lamp, and store a diagnostic trouble code or diagnostic
trouble codes which identify the problem areas to aid
the technician in making repairs.
See "Introduction"
Section "6E2" for more information on using the
diagnostic function
of the ECM.
For service, this ECM is replaced as a complete unit.
There are no serviceable parts in the
ECM. The
calibrations are stored in the
ECM in the Electronic
Erasable Programmable Read Only Memory
(EEPROM).
ENGINE CONTROL MODULE (ECM)
FUNCTION
This ECM supplies either 5 to 12 volts to power various
sensors
or switches. This is done through resistances
in the
ECM which are so high in value that a test light
Fig. 6E2-50

6E2-1 02 DRIVEABILITV AND EMISSIONS
Throttle Position (TP) Sensor (Fig. 6E2-53)
The Throttle Position (TP) Sensor is a potentiometer
connected to the throttle shaft on the Throttle Body
(TB). The TP sensor electrical circuit consists of a 5
volts supply line (signal line) and a ground line,
provided by the Engine Control Module (ECM).
By
monitoring the voltage on the signal line the ECM
calculates throttle position. As the TB angle is changed
(accelerator pedal moved), the output
of TP sensor
also changes.
At a closed throttle position, the output
of the TP sensor is low (approximately 5volt). As the TB
opens, the output increases so that, at wide-open
throttle, the output voltage
will be between 4 and 5
volts.
The
ECM can determine fuel delivery based on TB
angle (driver demand). A broken or loose TP sensor
can cause intermittent bursts of fuel from the injector,
and
an unstable idle, because the ECM thinks the
throttle is moving. A problem in any
of the TP sensor
circuits should set a diagnostic trouble code
(DTC) 21.
Once a DTC is set, the ECM will use an artificial default
valueforTP sensor. A high idle will result when DTC 21
is set.
See
"On-Vehicle Service" for replacement or
adjustment
of TP sensor.
ECM
~--2. Throttle position
sensor (TPS)
Fig. 6E2-53
Manifold Absolute Pressure (MAP) Sensor (Fig.
6E2-54)
The Manifold Absolute Pressure (MAP) sensor
measures the changes in the intake manifold pressure
which result
from engine load and speed changes, and
converts this to a voltage output.
A closed throttle on engine coast
down would produce
a relatively
low MAP output, while a Wide Open
Throttle would produce a high output. MAP is the
OPPOSITE of what would be measured on a vacuum
gage. When manifold pressure is high, vacuum is low.
The
MAP sensor is also used to measure barometric
pressure under contain conditions, which
allows the
ECM to automatically adjust for different altitudes. The
ECM sends a 5 volts reference signal to the MAP
sensor. As the manifold pressure changes, the
electrical resistance
of the sensor also changes. By
monitoring the sensor output voltage, the ECM knows
the manifold pressure.
A higher pressure,
low vacuum (high voltage) requires
more fuel, while a lower pressure, higher vacuum (low
voltage) requires less
fuel.
A failure in the MAP sensor circuit should set a DTC 33.
Map sensor
Fig. 6E2-54
Vehicle Speed Sensor (VSS)
The Vehicle Speed Sensor, sends a pulsing voltage
signal to the
ECM, which the ECM converts to miles per
hour. This sensor helps to control the
operation
of the idle air control system.
See
ELECTRICAL DIAGNOSIS (SECTION 8A) for more
information.
Knock Sensor (KS) (DOHC only)
The Knock Sensor is mounted in the engine block.
When abnormal engine vibrations (spark knock) are
present, the sensor produces a voltage signal, which is
sent to the knock sensor module.
See
"Knock Sensor System," Section "6E2-C5" for
further information on the knock sensor system.
Air Conditioning (A/C) Request Signal
This signal tells the ECM that the Air Conditioning (A/C)
selector switch is turned
"ON". The ECM uses this to
adjust the idle speed, before turning
"ON" the A/C
clutch.
If this signal is not available to the ECM, the A/C
compressor will be inoperative.
See "A/C Compressor Clutch Control System", Section
"6E2-C1 0" for A/C wiring diagrams and diagnosis of
A/C electrical system.
Power Steering Pressure (PSP) Switch
This switch tells the ECM that the vehicle is in a parking
maneuver. The
ECM uses this information to
compensate
for the additional engine load by moving
the idle air control valve. The
ECM will also turn "OFF"
the A/C clutch when high pressure is detected.
•

Park/Neutral Position (PNP) Switch (Auto Only)
The Park/Neutral position (PNP) switch indicates to the
Engine Control Module
(ECM) when the transmission
is in park, neutral
or drive. This information is used for
the exhaust gas recirculation, and the idle air control
valve operation.
NOTE:
• Vehicle
should not be driven with PNP switch
disconnected,
as idle quality will be affected and a
possible false diagnostic trouble code
(DTC) 24
(vehicle speed sensor).
DRIVEABILITY AND EMISSIONS 6E2-103
See DIAGNOSIS AND GENERAL SERVICE Section for
more information on the PNP switch. The PNP switch is
part
of the neutral/start and backup light switch
assembly mounted on the transmission.
See CHART C-
1 A for PNP switch check.
DIAGNOSIS
To read the DTC(s), use a "Scan tool" or ground the
diagnostic test terminal,
with the engine not running
and the ignition
"ON". The "Check Engine" malfunction
indicator lamp
will flash DTC 12 three times and then
flash each
DTC stored in memory three times. All
DTC(s) stored in memory will have been read when
DTC 12 is flashed again.
No new
DTC(s) can be stored when in the diagnostics
test mode (diagnostics lead grounded). This
eliminates confusion while the system is being
serviced.
To clear the
DTC(s) from memory:
• Ignition "OFF".
•
Disconnect main fuse located in the under hood
fuse/relay center near the battery.
Since the ECM can have a failure which may affect only
one circuit, following the diagnostic procedures in this
section
will determine which circuit has a problem and
where
it is.
If a diagnostic chart indicates thatthe ECM connections
or ECM is the cause of a problem, and the ECM is
replaced,
but does not correct the problem, one of the
following may be the reason.
• There is a problem with the ECM terminal
connections-The diagnostic chart will say ECM
connections or ECM. The terminals may have to
be removed from the connector in order to check
them properly.
• The ECM is not correct for the Vehicle-Ane
incorrect
ECM may cause a malfunction and may
set a DTC.
• The problem is intermittent -This means that
the problem is
not present at the time the system is
being checked.
In this case, refer to the
"Symptoms" portion of the manual and make a
careful physical inspection
of all portions of the
system involved.
• Shorted solenoid, relay coil, or harness
Solenoid and relays are turned "ON" and "OFF" by
the
ECM, using internal electronic switches called
"drivers".
Each driver is part of a group of four,
called "quad-drivers". Failure of one driver can
damage any other driver in the set. A
shorted solenoid, relay coil, or harness in a l-EFT­
SHCI
computer will not damage the ECM, but will
cause the circuit and controlled component to be
inoperative. When the circuit fault is not present or
has been repaired, the "quad-driver" will again
operate in a normal manner due to its fault
protected design. If a fault has been repaired in a
circuit controlled by a "quad-driver", the original
ECM should be reinstalled and the circuit checked
for proper operation. ECM replacement will not be
necessary if the repaired circuit or component now
operates correctly.
J 34636 or BT-8405 testers or equivalent provide a fast,
accurate means
of checking for a shorted coil or a short
to battery positive voltage.
• The replacement ECM may be faulty-After the
ECM is replaced, the system should be re-checked
for proper operation. If the diagnostic chart again
indicates the
ECM is the problem, substitute a
known good
ECM. Although this is a rare
condition,
it could happen.
ENGINE CONTROL MODULE (ECM)
A faulty ECM will be determined in the diagnostic
charts.
ELECTRONICALL V ERASABLE
PROGRAMMABLE READ
ONL V MEMORY
A faulty electrically erasable programmable read only
memory, which is part of the ECM, will set a DTC 51.
ENGINE CONTROL MODULE (ECM)
INPUTS
All of the sensors and input switches can be diagnosed
by the use
of "Scan tool".
Following is a short description of how the sensors and
switches can be diagnosed by the use
"Scan tool". The
"Scan tool" can also be used to compare the values for
a normal running engine with the engine you're
diagnosing.

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.
•

wcAUTION:
' • When replacing the production Engine Control
Module
(ECM) with a service ECM (controller),
it is important to transfer the broadcast
diagnostic
trouble code and production ECM
number to the service ECM label. Please do not
record on ECM cover. This will allow positive
identification
of ECM parts throughout the
service
life of the vehicle.
DRIVEABILITV AND EMISSIONS 6E2-1 05
\fCAUTION:
' • To prevent internal ECM damage, the ignition
must be
"OFF" when disconnecting or
reconnecting power
to ECM (for example;
battery cable, ECM pigtail, ECM fuse, jumper
cables etc.)
ENGINE CONTROL MODULE (ECM) REPLACEMENT
Removal steps 1. Negative battery cable 2. Lower trim panel at console
3. A/C Heater transfer tube ECM 4. ABS controller electrical
controller
5. ABS controller 6. Four fasteners for ECM bracket
7. ECM electrical connectors
8. ECM from under dash bracket still attached
Installation steps To install, follow the removal steps
reverse in the order.
Fig. 6E2-55
EJ REMOVAL
1. Negative battery cable
2. Lower trim panel at console (4 fasteners)
3. Air Conditioning Heater transfer tube
4. ABS controller electrical connector (1) (if
equipt)
5. ABS controller (4 fasteners) (if equipt)
6. Four (4) fasteners for ECM bracket
7. ECM
electrical connectors (2)
8. ECM from under dash, bracket
still attached
NOTE:
To prevent possible Electronic Discharge damage
to the ECM, Do not touch the connector pins or
soldered components on the circuit board.
I•+! INSTALLATION
1. ECM and bracket under dash
2. Four (4) fasteners and tighten
3. Two (2) ECM electrical connectors
4. ABS controller and four (4) fasteners (if equipt)
5. ABS controller electrical connector (if equipt)
6. Air Conditioning Heater transfer tube
7. Lower trim panel at console (4 fasteners)
8. Negative battery
cable
Functional
Check
1. Turn ignition "ON".
2. Enter diagnostics test mode.
A.
Allow Diagnostic Trouble Code (DTC) 12 to
flash four times to verify no other DTC(s) are
present. This indicates the reprogrammed
ECM is functioning properly.
B. If DTC 51 occurs, or if the malfunction
indicator lamp is "ON" constantly with no
DTC(s), the
ECM is defective.
• If it is necessary to replace the ECM, follow
the previous removal instructions.
ENGINE COOLANT TEMPERATURE (ECT)
SENSOR
Fig. 6E2-56

New or service sensors will already have the
compound
applied to the threads. If a sensor is
removed
from an engine and iffor any reason it
is to be reinstalled, the threads must have anti­
seize compound
applied before reinstallation.
•
Apply anti-seize compound or equivalent to
threads of oxygen sensor if necessary.
• Tighten the oxygen sensor to the specified
torque.
1~1 Torque N·m (lb·ft) 55 (40)
1. H02S wiring connector
THROTTLE POSITION (TP) SENSOR
Fig. 6E2-59
E) REMOVAL
Preparation: • Battery negative cable.
1. Throttle Position (TP) sensor wiring connector
2. TP sensor fixing screw
3. TP sensor
I••IINSTALLATION
3. TP sensor
2. TP sensor fixing screw
• Tighten the fixing screw to the specified torque.
~~~ Torque N·m (lb·in) I 2 (18)
• Use a "Scan tool" to check TP sensor output
voltage with throttle closed, should be under
0.85 volts. If over 0.85 volts, check for binding
throttle shaft, or TP sensor lever. If all OK,
replace TP sensor.
1.
TP sensor wiring connector
DRIVEABILITY AND EMISSIONS 6E2-1 07
MANIFOLD ABSOLUTE PRESSURE
(MAP) SENSOR
1. Vacuum hose
) 0~
2 .• ,.~,,~,~
conne~ JJJ
4. Sensor
Fig. 6E2-60
E) REMOVAL
Preparation: • Battery negative cable.
1. Vacuum hose
2. Electrical connector
3. Attaching screws
4. Sensor
I••IINSTALLATION
4. Sensor
3. Attaching screws
2. Electrical connector
1. Vacuum hose
VEHICLE SPEED SENSOR (VSS)
Refer to INSTRUMENT PANEL CLUSTER AND
CONSOLE of this manual for replacement of vehicle
speed sensor located in instrument panel.
POWER STEERING PRESSURE (PSP)
SWITCH
Refer to STEERING, SUSPENSION, TIRES AND
WHEELS for service of the power steering pressure
switch.
PARK/NEUTRAL
SWITCH POSITION
(PNP}
See
Section AUTOMATIC TRANSMISSION GENERAL
INFORMATION Section for park/neutral position
switch.
"On-Vehicle Service" and adjustment
procedures are
also listed there.