ignition ISUZU TROOPER 1995 Workshop Manual

DRIVEABILITY AND EMISSIONS 6E2-89
SECTION B
SYMPTOMS
CONTENTS
Important Preliminary Checks . . . . . . . . . 6E2-89
Before Starting . . . . . . . . . . . . . . . . . . . . . . 6E2-89
Symptom . . . . . . . . . . . . . . . . . . . . . . . . . . . 6E2-89
Visual/Physical Check . . . . . . . . . . . . . . . . 6E2-89
lntermittents . . . . . . . . . . . . . . . . . . . . . . . . 6E2-90
Hard Start . . . . . . . . . . . . . . . . . . . . . . . . . . 6E2-90
Surges and/or Chuggles .............. 6E2-91
Lack of Power, Sluggish, or Spongy . . . . 6E2-92
Detonation/Spark Knock .............. 6E2-92
Hesitation, Sag, Stumble . . . . . . . . . . . . . 6E2-93
Cuts Out, Misses . . . . . . . . . . . . . . . . . . . . . 6E2-93
Rough, Unstable, or Incorrect Idle,
Stalling ............................. 6E2-94
Poor Fuel Economy . . . . . . . . . . . . . . . . . . . 6E2-95
Excessive Exhaust Emissions or Odors .. 6E2-96
Backfire . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6E2-96
Dieseling, Run-on .................... 6E2-97
Restricted Exhaust System
Check (CHART B-1) ................... 6E2-98
IMPORTANT PRELIMINARY CHECKS
BEFORE STARTING
Before using this section you should have performed
the on-board diagnostic system check and determined
that:
1. The engine control module and "Check Engine"
malfunction indicator lamp are operating
correctly.
2. There are no diagnostic trouble codes stored, or
there is a diagnostic trouble code but no "Check
Engine" malfunction indicator lamp.
SYMPTOM
Verify the customer complaint, and locate the correct
symptom in the
table of contents. Check the items
indicated under
that symptom.
VISUAL/PHYSICAL CHECK
Several of the symptom procedures call for a Careful
Visual/Physical
Check. The importance of this step
cannot
be stressed too strongly -it can lead to
correcting a
problem witho'ut further checks and can
save
valuable time. This check should include: •
Engine control
module grounds for being clean,
tight and in their proper location.
•
Vacuum hoses for splits, kinks, and proper
connections,
as shown on "Vehicle Emission
Control Information" label. Check thoroughly for
any type of leak or restriction.
• Air leaks atthrottle body mounting area and intake
manifold
sealing surfaces.
• Ignition wires for cracking, hardness, proper
routing and carbon tracking.
• Wiring for proper connections, pinches and cuts.
• Fuel lines for being pinched or misrouted.

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.

6E2-92 DRIVEABILITY AND EMISSIONS
LACK OF POWER, SLUGGISH OR SPONGY
Definition: Engine delivers less than expected power.
Little or no increase in speed when
accelerator
pedal is pushed down part
way.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
described at start of "Symptoms," Section "6E2-
B."
•
Compare customer's car to similar unit. Make sure
the
vehicle has an actual problem.
• Remove air filter and check air filter for dirt, or for
being plugged. Replace as necessary.
FUEL SYSTEM
• CHECK: Rescricted fuel filter.
• CHECK: Fuel pressure, use CHART A-7.
• CHECK: Contaminated fuel.
• CHECK: Fuel injectors are correct for the vehicle.
IGNITION SYSTEM
• CHECK: Ignition timing, using "Scan tool".
• CHECK: Knock sensor system for excessive spark
retard activity. Refer to CHART
C-5. Use
"Scan tool".
• CHECK: Secondary voltage using an oscilloscope
or a spark tester J 26792 (ST-125), or
equivalent, to check for a weak coil.
ADDITIONAL CHECKS
• CHECK: Engine control module grounds for being
clean,
tight and in their proper locations.
See engine control module wiring
diagrams.
• CHECK: Exhaust gas recirculation operation for
being open or partly open all the time.
- Refer to CHART
C-7.
• CHECK: Generator output voltage. Repair if less
than 9
or more than 16 volts.
• CHECK: Exhaust system for possible restriction.
Refer
to CHART B-1.
-Inspect exhaust system for damaged
or collapsed pipes.
-
Inspect muffler for heat damage or
possible internal failure.
• CHECK: Torque converter clutch for proper
operation. Refer
to AUTOMATIC
TRANSMISSION
(SECTION 7A).
ENGINE MECHANICAL
• CHECK: Engine valve timing and compression.
• CHECK: Engine for correct or worn camshaft.
Refer
to ENGINE MECHANICAL
DIAGNOSIS
(SECTION 6A).
DETONATION/SPARK KNOCK
Definition: A mild to severe ping, usually worse under
acceleration. The engine makes sharp
metallic knocks that change with throttle
opening.
Sounds like popcorn popping.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
Low engine coolant.
Restricted air
flow to radiator, or restricted
water flow through radiator.
Correct engine
coolant solution should be a 50/
50 mix of anti-freeze engine coolant (or
equivalent) and water.
described at start
of "Symptoms," Section "6E2-FUEL SYSTEM
B."
•
Park/Neutral position switch. Be sure "Scan tool"
indicates drive with gear selector in drive or
overdrive. Use
CHART C-1A.
• If "Scan tool" readings are normal (see facing page
of on-board diagnostic system check) and there
are no engine mechanical faults,
fill fuel tank with a
gasoline
that has a minimum octane reading of 87
and revaluate vehicle performance.
• CHECK: Exhaust gas recirculation system for not
opening. Use CHART C-7.
COOLING SYSTEM
• Check for obvious overheating problems:
• NOTICE: To determine if the condition is caused by
a rich
or lean system, the car should be
driven at the speed
of the complaint.
Monitoring
LT. Fuel Trim will help
identify problem.
Lean-
LT. Fuel Trim above 142. Refer to
"Diagnostic Aids" on facing page of
diagnostic trouble code 44.
Rich-LT. Fuel Trim below 118. Refer to
"Diagnostic Aids" on facing page of
diagnostic trouble code 45.
• CHECK: Fuel pressure, use CHART A-7.
..

IGNITION SYSTEM
• CHECK: Spark plugs for proper heat cause. Refer
to Owner's Manual.
• CHECK: Ignition timing, using a "Scan tool".
ENGINE MECHANICAL
• CHECK: For excessive oil in the combustion
chamber. -
Valve oil seals for leaking.
• CHECK: Combustion chambers for excessive
carbon
build up. Remove carbon with top
engine cleaner and follow instructions on
can.
DRIVEABILITY AND EMISSIONS 6E2-93
• CHECK: Combustion chamber pressure by
performing a compression test.
See
ENGINE MECHANICAL DIAGNOSIS
(SECTION 6A).
• CHECK: For incorrect basic engine parts such as
cam, heads, pistons, etc.
HESITATION, SAG, STUMBLE
Definition: Momentary lack of response as the
accelerator is pushed down. Can occur at
all car speeds. Usually most severe when
first trying
to make the car move, as from a
stop sign. May cause engine to
stall if
severe enough.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
described at start of "Symptoms," Section "6E2-
B."
SENSORS
• CHECK: Throttle position sensor for binding or
sticking. Voltage should increase at a
steady
rate as throttle is moved toward
Wide Open Throttle.
• CHECK: Manifold absolute pressure sensor-use
CHART C-10.
FUEL SYSTEM
• CHECK: Fuel pressure, use CHART A-7.
• CHECK: Fuel injectors are correct for vehicle.
• CHECK: Contaminated fuel.
• CHECK: Evaporative emission canister purge
system
for proper operation. Refer to
"Evaporative Emission Control System,"
Section "6E2-C3."
IGNITION SYSTEM
• CHECK: Spark plugs for being fouled, or for faulty
secondary wiring.
• CHECK: Ignition timing, using a "Scan tool".
• CHECK: Ignition system ground.
ADDITIONAL CHECKS
• CHECK: Exhaust gas recirculation operation, use
CHART
C-7.
• CHECK: Engine thermostat functioning correctly
and proper heat range.
• CHECK: Generator output voltage. Repair if less
than 9 or more than 16 volts.
CUTS OUT, MISSES
Definition: Steady pulsation or jerking that follows
engine speed, usually more pronounced
as engine load increases, not normally felt
above 1500 revolution per minute or 48
kph
(30 mile per hour). The exhaust has a
steady spitting sound at
idle or low speed.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
described at start of "Symptoms," Section "6E2-
B."
IGNITION SYSTEM
• Check for cylinder miss by:
1. Start engine, allow engine to stabilize then
disconnect
idle air control motor. Remove
one spark
plug wire at a time, using insulated
pliers.
CAUTION: Do not perform this test for
more than 2 minutes,
as this test may
cause damage to the three
way
catalytic converter.
2. If there is a revolution per minute drop on all
cylinders (equal
to within 50 revolution per
minute), go
to "Rough, Unstable, or Incorrect
Idle, Stalling"
symptom. Reconnect idle air
control valve.

IGNITION SYSTEM
• CHECK: Ignition timing, using a "Scan tool".
• CHECK: Ignition system; wires, plugs, electronic
ignition, etc.
ENGINE MECHANICAL
• CHECK: Perform a cylinder compression check.
See ENGINE MECHANICAL DIAGNOSIS
(SECTION 6).
• CHECK: For correct camshaft or weak valve
springs.
ADDITIONAL CHECKS
• CHECK: Manifold absolute pressure sensor.
Refer to
CHART C-10.
• CHECK: Throttle linkage for sticking or binding.
• CHECK: Park/neutral position switch circuit. See
CHART C-1A,
or use "Scan tool" and be
sure
tool indicates vehicle is in drive with
gear selector in drive or overdrive.
DRIVEABILITY AND EMISSIONS 6E2-95
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
Idle air control operation, use CHART C-
2C.
Exhaust gas recirculation valve. There
should be no exhaust gas recirculation at
idle. Refer to CHART C-7A.
Air conditioning (A/C) signal to engine
control module, "Scan tool" should
indicate A/C is being requested when
ever
A/C is selected. If problem exists
with A/C "ON," check A/C system
operation
CHART C-10.
Positive crankcase ventilation valve for
proper operation. Refer to "Positive
Crankcase Ventilation (PCV),"
Section
"6E2-C13."
For broken motor mounts.
Generator output
voltage. Repair if less
than 9 or more than 16 volts.
POOR FUEL ECONOMY
Definition: Fuel economy, as measured by an actual
road test, is noticeably lower than
expected.
Also, fuel economy is
noticeably lower than it was on this car at
one time,
as previously shown by an actual
road test.
PRELIMINARY CHECKS
• Perform the careful visual checks as described at
start
of "Symptoms," Section "6E2-B."
• Visually (physically)
check: Vacuum hoses for
splits, kinks, and proper connections as shown on
"Vehicle Emission Control Information" label.
• Check
owner's driving habits.
Is A/C "ON" full time (Defroster mode "ON")?
Are tires at correct pressure?
Are
excessively heavy loads being carried?
Is acceleration too much, too often?
• Check air cleaner filter for dirty or being plugged.
IGNITION SYSTEM
• CHECK: Ignition timing. Refer to "Vehicle
Emission Control Information" label.
• CHECK: Spark plugs. Remove spark plugs, check
for wet plugs, cracks, wear, improper
gap, burned electrodes, or heavy
deposits. Repair or
replace as necessary.
COOLING SYSTEM
• CHECK: Engine coolant level.
• CHECK: Engine thermostat for faulty part (always
open) or for wrong heat range. Refer to
ENGINE COOLING (SECTION 68).
ENGINE MECHANICAL
• CHECK: Compression. See ENGINE MECHANICAL
DIAGNOSIS
(SECTION 6A).
ADDITION CHECKS
• CHECK:
• CHECK:
• CHECK:
• CHECK:
• CHECK:
TCC operation (A/T). Use CHART C-8. A
"Scan tool" should indicate a revolution
per minute drop, when the TCC is
commanded
"ON".
For exhaust system restriction.
For proper
calibration of speedometer.
Induction system and crankcase for air
leaks.
Fuel
injectors are correct for the vehicle.

6E2-96 DRIVEABILITY AND EMISSIONS
EXCESSIVE EXHAUST EMISSIONS OR ODORS
Definition: Vehicle fails an emission test. Vehicle has
excessive
"rotten egg" smell. Excessive
odors
do not necessarily indicate
excessive emissions.
PRELIMINARY CHECKS
• Perform on-board diagnostic system check.
• IF EMISSION TEST shows excessive CO and
hydrocarbon check items which cause car to run
RICH (Long Term Fuel Trim less than 118), refer to
"Diagnostic Aids" on facing page of diagnostic
trouble code (DTC) 45.
• If EMISSION TEST shows excessive NOx, check
items which cause car
to run lean or too hot.
COOLING SYSTEM
• If the "Scan tool" indicates a very high engine
coolant temperature and the system is running
lean:
CHECK: Engine coolant level
CHECK: Engine thermostat for faulty part
(always open) or for wrong heat range. Refer
to
ENGINE COOLING (SECTION 68).
CHECK: Cooling fan operation.
FUEL SYSTEM
• NOTICE: If the system is running rich (L.T. Fuel
Trim near 118), refer to "Diagnostic Aids"
on facing page
of DTC 45.
-
If the system is running lean (L.T. Fuel
Trim near 142) refer to "Diagnostic
Aids" on facing page of DTC 44.
• CHECK: For properly installed fuel cap.
• CHECK: Fuel pressure. Use CHART A-7.
• CHECK: Canister for fuel loading. Refer to
"Evaporative Emission Control System,"
Section
"6E2-C3."
IGNITION SYSTEM
• CHECK: Ignition timing. Refer to "Vehicle
Emission Control Information" label.
• CHECK: Spark plugs, plug wires, and ignition
components. Refer to
ENGINE
ELECTRICAL (SECTION 6D).
ADDITIONAL CHECKS
• CHECK: For vacuum leaks.
• CHECK: Exhaust gas recirculation valve for not
opening. Use CHART C-7.
• CHECK: For lead contamination of three way
catalytic converter (look for the removal
of fuel filler neck restrictor).
• CHECK: Carbon build-up. Remove carbon with
top engine cleaner. Follow instructions
on can.
• CHECK: PCV valve for being plugged, stuck or
blocked PCV hose or fuel in the
crankcase.
BACKFIRE
Definition: Fuel ignites in intake manifold, or in
exhaust system, making
loud popping
noise.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
described at start of "Symptoms," Section "6E2-
B."
IGNITION SYSTEM
• CHECK: Proper ignition coil output voltage with
spark tester J26792 or equivalent (ST-
125).
• 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: Spark plug wires for crossfire, also
inspect electronic ignition, spark plug
wires, and proper routing of plug wires.
• CHECK: Ignition timing. Refer to "Vehicle
Emission Control Information" label.
• CHECK: If an intermittent condition exists in the
ignition system, see
"Ignition System/
IGNITION CONTROL," Section "6E2-C4"
or ENGINE ELECTRICAL (SECTION 6D).
ENGINE MECHANICAL
• CHECK: Compression- Look for sticking or leaking
valves.
• CHECK: Valve timing, refer to ENGINE
MECHANICAL DIAGNOSIS (SECTION
6A).
• CHECK: Intake and exhaust manifold passages for
casting
flash.
FUEL SYSTEM
• CHECK: Perform fuel system diagnosis check, see
CHART A-7.

DRIVEABILITV AND EMISSIONS 6E2-97
ADDITIONAL CHECKS • CHECK: Intake and exhaust manifold for casting
• CHECK: Exhaust gas recirculation (EGR) gasket flash.
for faulty or loose fit.
• CHECK: EGR operation for being open all the time.
Refer to
"EGR," CHART C-7.
DIESELING, RUN-ON
Definition: Engine continues to run after key is turned
"OFF", but runs very roughly. If engine
runs
smoothly, check ignition switch and
adjustment.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
described at start of "Symptoms," Section "6E2-
B."
FUEL SYSTEM
• CHECK: Injectors for leaking. Refer to "Fuel
System Diagnosis" CHART A-7.

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

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.