1998 ISUZU TROOPER Service Repair Manual

wheel bolts child lock automatic transmission lane assist washer fluid heater

Page 1369 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±252
ENGINE DRIVEABILITY AND EMISSIONS
passage and on the IAC pintle, and excessive deposits
in the throttle bore and on the throttle plate.
Large vacuum leak ± Check for a condition that causes

6E±252
ENGINE DRIVEABILITY AND EMISSIONS
passage and on the IAC pintle, and excessive deposits
in the throttle bore and on the throttle plate.
Large vacuum leak ± Check for a condition that causes
a large vacuum leak, such as an incorrectly installed or
faulty PCV valve or a disconnected brake booster
hose.Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.
DTC P1508 ± IAC System Low RPM
StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Start the engine.
2. Turn all accessories ªOFFº(A/C, rear defroster,
etc).
3. Using a Tech 2, command RPM up to 1500, down to
500, and the up to 1500 while monitoring the
ªEngine Speedº on the Tech 2.
NOTE: This Tech 2 command may cause the engine to
ªcut outº when RPM goes above 1500. If this occurs,
the ªcutting outº will stop when the Tech 2 command for
the test is discontinued, or if the Tech 2 command is
changed to less than 1500 RPM.
Does the ªEngine Speedº remain within the specified
value of the ªDesired Idleº for each RPM command?
+ 50 RPM
No trouble
found. Go to
Diagnostic
Aids
Go to Step 3
31. Disconnect the IAC.
2. Install IAC Node Light 5-8840-2312-0 or equivalent.
3. With the engine running, command RPM up to
1500, down to 500, and then up to 1500 while
observing the node light.
NOTE: This Tech 2 command may cause the engine to
ªcut outº when RPM goes above 1500. If this occurs,
the ªcutting outº will stop when the Tech 2 command for
the test is discontinued, or if the Tech 2 command is
changed to less than 1500 RPM.
Does each node light cycle red and green (never
ªOFFº)?
ÐGo to Step 5Go to Step 4
41. Check the following circuits for an open, short to
voltage, short ground, or poor connections at the
PCM:
IAC ªAº Low.
IAC ªAº High.
IAC ªBº Low.
IAC ªBº High.
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 8

Page 1370 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±253 ENGINE DRIVEABILITY AND EMISSIONS
DTC P1508 ± IAC System Low RPM
StepNo Ye s Value(s) Action
5Visually/physically inspect for following conditions:
Restricted air intake system. C

Page 1371 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±254
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1509 IAC System High RPM
T321115
Circuit Description
The powertrain control module (PCM) controls engine
idle speed by adjustin

6E±254
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1509 IAC System High RPM
T321115
Circuit Description
The powertrain control module (PCM) controls engine
idle speed by adjusting the position of the idle air control
(IAC) motor pintle. The IAC is a bi-directional stepper
motor driven by two coils. The PCM applies current to the
IAC coils in steps (counts) to extend the IAC pintle into a
passage in the throttle body to decrease air flow. The
PCM reverses the current to retract the pintle, increasing
air flow. This method allows highly accurate control of idle
speed and quick response to changes in engine load. If
the PCM detect a condition where too high of an idle
speed is present and the PCM is unable to adjust idle
speed by increasing the IAC counts, DTC P1509 will set,
indicating a problem with the idle control system.
Conditions for Setting the DTC
No Tech 2 test is being run.
None of these DTCs are set: TP sensor, VSS, ECT,
EGR, fuel system, MAF, MAP, IAT, canister purge,
injector control or ignition control.
Barometric pressure is above 75 kPa.
Engine coolant temperature is above 50C (120F).
Engine speed is more than 100-200 RPM lower than
desired idle, based upon coolant temperature.
The engine has been running for at least 125 seconds.
Vehicle speed is less than 1 mph.
Canister purge duty cycle is above 10%.
Ignition voltage is between 9.5 volts and 16.7 volts.
Engine speed is lower than desired idle.All of the above conditions are met for 5 seconds.
Action Taken When the DTC Sets
The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
DTC P1509 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at PCM or IAC motor ± Inspect
harness connectors for backed-out terminals,
improper mating, broken locks, improperly formed or
damaged terminals, and poor terminal-to-wire
connection.
Damaged harness ± Inspect the wiring for damage.
Vacuum leak ± Check for a condition that causes a
vacuum leak, such as disconnected or damaged
hoses, leaks at the EGR valve and the EGR pipe to the
intake manifold, leaks at the throttle body, faulty or
incorrectly installed PCV valve, leaks at the intake
manifold, etc.

Page 1372 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±255 ENGINE DRIVEABILITY AND EMISSIONS
Throttle body ± Check for sticking throttle plate. Also
inspect the IAC passage for deposits or objects which
keep the IAC pintle from fully extending.
Rev

6E±255 ENGINE DRIVEABILITY AND EMISSIONS
Throttle body ± Check for sticking throttle plate. Also
inspect the IAC passage for deposits or objects which
keep the IAC pintle from fully extending.
Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how oftenthe condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.
DTC P1509 ± IAC System High RPM
StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
21. Start the engine.
2. Turn all accessories ªOFFº (A/C, rear defroster,
etc.).
3. Using a Tech 2, command RPM up to 1500, down to
500, and then up to 1500 while monitoring ªEngine
Speedº on the Tech 2.
NOTE: This Tech 2 command may cause the engine to
ªcut outº when RPM goes above 1500. If this occurs,
the ªcutting outº will stop when the Tech 2 command for
the test is discontinued, or if the Tech 2 command is
changed to less than 1500 RPM.
Does the ªEngine Speedº remain within the specified
value of ªDesired Idleº for each RPM command?
+ 50 RPM
No trouble
found. Go to
Diagnostic
Aids
Go to Step 3
31. Disconnect the IAC.
2. Install IAC Node Light 5-8840-2312-0 or equivalent.
3. With the engine running, command RPM up to
1500, down to 500, and then up to 1500 while
observing the node light.
NOTE: This Tech 2 command may cause the engine to
ªcut outº when RPM goes above 1500. If this occurs,
the ªcutting outº will stop when the Tech 2 command for
the test is discontinued, or if the Tech 2 command is
changed to less than 1500 RPM.
Does each node light cycle red and green (never
ªOFFº)?
ÐGo to Step 5Go to Step 4
41. Check the following circuits for an open, short to
voltage, short ground, or poor connections at the
PCM:
IAC ªAº Low
IAC ªAº High
IAC ªBº Low
IAC ªBº High
2. If a problem is found, repair as necessary.
Was a problem found?
ÐVerify repairGo to Step 8
5Visually/physically inspect for following conditions:
Vacuum leaks.
Throttle plate or throttle shaft for binding.
Accelerator and cruise control cables for being
misadjusted or for binding.
Faulty, missing, or incorrectly installed PCV
valve.
Do any of the above require a repair?
Ð
Refer to
appropriate
section for
on-vehicle
service
Go to Step 6

Page 1373 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±256
ENGINE DRIVEABILITY AND EMISSIONS
DTC P1509 ± IAC System High RPM
StepNo Ye s Value(s) Action
61. Check for a poor connection at the IAC harness
connector.
2. If a problem is found,

Page 1374 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±257 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1618 Serial Peripheral Interface (SPI) PCM
Interprocessor Communication Error
Circuit Description
The serial peripheral interfa

6E±257 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1618 Serial Peripheral Interface (SPI) PCM
Interprocessor Communication Error
Circuit Description
The serial peripheral interface (SPI) communication is
used internally by the PCM to send messages between
the engine processor and the automatic transmission
processor. Included in each message sent between the
two-processors is a checksum of the message. Both the
engine processor and automatic transmission processor
will compare this check sum value with the calculated
value. If the checksums don't match, the processor will
view the new data as being corrupted and ignore the
values. The processor will then use the previous
message. The receiving processor will then send a
message to the sending processor informing it that it's
last message was corrupted.
Conditions for Setting the DTC
Battery voltage is above 9.0 V for 2 seconds.
The PCM detects an internal program fault (check sum
of data communications error).Check sum fault present for 3 out 6 seconds.
No TCM resets for 2 seconds.
Action Taken When the DTC Sets
The PCM will flash the ªCheck Transº lamp the first
time the fault is detected.
The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
The automatic transmission will operate in the ªsafety
modeº to protect the mechanical parts of the
transmission. Shift quality and/or gear changes may
not be normal.
Conditions for Clearing the MIL/DTC
DTC P1618 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
DTC P1618 ± Serial Peripheral Interface (SPI) PCM Interprocessor
Communication Error
StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Is the EEPROM calibration the latest version
available?
ÐGo to Step 4Go to Step 3
3Reprogram the PCM with the latest available
calibrations.
Does DTC 1618 re-appear when the
OBD System
Check
is repeated?ÐGo to Step 4
Repair
completed
4Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?ÐVerify repairÐ

Page 1375 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±258
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1625 PCM Unexpected Reset
Circuit Description
The powertrain control module (PCM) monitors
unexpected PCM reset. This will not

Page 1376 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±259 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1640 Driver-1-Input High Voltage
Circuit Description
Output driver modules (ODMs) are used by the
powertrain control module (PC

6E±259 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P1640 Driver-1-Input High Voltage
Circuit Description
Output driver modules (ODMs) are used by the
powertrain control module (PCM) to turn ªONº many of
the current-driven devices that are needed to control
various engine and transmission functions. Each ODM is
capable of controlling up to 7 separate outputs by
applying ground to the device which the PCM is
commanding ªON.º
Unlike the Quad Driver Modules (QDMs) used in prior
model years, ODMs have the capability of diagnosing
each output circuit individually. DTC P1640 set indicates
an improper voltage level has been detected on an ODM
output.
Since A/C is an option, No A/C will cause the air
conditioning clutch relay output to always fault. If a fault is
seen on the air conditioning clutch relay output, it will not
be logged as a fault until the A/C request input interrupts a
high voltage, indicating that A/C has been installed.
Conditions for Setting the DTC
Ignition ªON.º
Engine running.
No DTC 1618.
Ignition voltage is above 13.2 volts for 4 seconds.
Output voltage does not equal ignition voltage when
output is ªOFFº or output voltage is not less than 1 volt
when output is ªON.º
Above conditions occur for at least 1 second.
Action Taken When the DTC Sets
The PCM will not illuminate the malfunction indicator
lamp (MIL).
The PCM will store conditions which were present
when the DTC was set as Failure Records only. This
information will not be stored as Freeze Frame data.
Conditions for Clearing the MIL/DTC
DTC P1640 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
Check for the following conditions:
Poor connection at PCM ± Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.
Damaged harness ± Inspect the wiring harness for
damage, If the harness appears to be OK, disconnect
the PCM, turn the ignition ªONº and observe a
voltmeter connected to the suspect driver circuit at the
PCM harness connector while moving connectors and
wiring harnesses relates to the MIL. A change in
voltage will indicate the location of the fault.
Poor connection at component ± Examine for
damaged connectors, unplugged connector, or
damaged terminals at the following locations:
Instrument cluster harness, canister purge solenoid,
A/C clutch relay. An open ignition feed circuit at any of
these components will cause DTC P1640 to be set.
Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs. This
may assist in diagnosing the condition.
The following PCM pins are controlled by output driver
modules (ODMs):
A13 ± ªCheck Engine Lampº
A14 ± SVS (ºCheck Transº)
B14 ± A/C Clutch
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
6. The Tech 2 Driver Module Status indicates the PCM
pin that is affected.
11. The Tech 2 may indicate ªshort circuitº even when
the problem is an open circuit. The cause of an
open circuit may be in the component itself-lamp,
purge, solenoid, or A/C compressor relay.
13.A short to ground on the ignition side of the
component will blow the fuse. Since the fuse was
checked in Step 4, a short to ground would be
between the affected component and the PCM.

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