1998 ISUZU TROOPER Service Repair Manual

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Page 1169 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±52
ENGINE DRIVEABILITY AND EMISSIONS
10.This vehicle is equipped with a PCM which utilizes
an electrically erasable programmable read only
memory (EEPROM). When the PCM is replaced,
the new PCM m

Page 1170 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±53 ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD) System Check
StepActionValue(s)Ye sNo
11. Ignition ªON,º engine ªOFF.º
2. Observe the malfunction indicator lamp (MIL or
ªCheck

6E±53 ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD) System Check
StepActionValue(s)Ye sNo
11. Ignition ªON,º engine ªOFF.º
2. Observe the malfunction indicator lamp (MIL or
ªCheck Engineº lamp).
Is the MIL (ªCheck Engineº lamp)ªON?º
ÐGo to Step 2
Go to No MIL
(ªCheck
Engineº lamp)
21. Ignition ªOFF.º
2. Install a Tech 2.
3. Ignition ªON.º
4. Attempt to display PCM engine data with the Tech 2.
Does the Tech 2 display PCM data?
ÐGo to Step 3Go to Step 8
31. Using the Tech 2 output tests function, select MIL
(ªCheck Engineº lamp) dash lamp control and
command the MIL (ªCheck Engineº lamp) ªOFF.º
2. Observe the MIL (ªCheck Engineº lamp).
Did the MIL (ªCheck Engineº lamp) turn ªOFF?º
ÐGo to Step 4
Go to MIL
(ªCheck
Engineº lamp)
On Steady
4Attempt to start the engine.
Did the engine start and continue to run?
ÐGo to Step 5
Go to Cranks
But Will Not
Run
5Select ªDisplay DTCsº with the Tech 2.
Are any DTCs stored?
ÐGo to Step 6Go to Step 7
6Are two or more of the following DTCs stored? P0107,
P0108, P0113, P0118, P0122, P0123, P0712.?
Ð
Go to
ªMultiple
PCM
Information
Sensor DTCs
Setº
Go to
applicable
DTC table
7Compare PCM data values displayed on the Tech 2 to
the typical engine scan data values.
Are the displayed values normal or close to the typical
values?
Ð
Refer
to
Typical
scan data
value
Refer to
indicated
Component
System
Checks
81. Ignition ªOFF,º disconnect the PCM.
2. Ignition ªON,º engine ªOFF.º
3. Check the Class 2 data circuit for an open, short to
ground, or short to voltage. Also, check the DLC
ignition feed circuit for an open or short to ground
and the DLC ground circuit for an open.
4. If a problem is found, repair as necessary.
Was a problem found?
ÐGo to Step 2Go to Step 9
9Attempt to display PCM data with the Tech 2.
Does the Tech 2 display PCM engine data?
ÐGo to Step 2Go to Step 10
10Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
Powertrain Control Module
(PCM) in On-Vehicle Service.
Is the action complete?ÐGo to Step 2Ð

Page 1171 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±54
ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
D06RW085
Circuit Description
When air conditioning and blower fan are selected, and if
the system has a sufficient refrige

Page 1172 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±55 ENGINE DRIVEABILITY AND EMISSIONS
Damaged harness±Inspect the wiring harness for
damage. If the harness appears to OK, observe the
A/C clutch while moving connectors and wiring
harnesses rel

6E±55 ENGINE DRIVEABILITY AND EMISSIONS
Damaged harness±Inspect the wiring harness for
damage. If the harness appears to OK, observe the
A/C clutch while moving connectors and wiring
harnesses related to the A/C. A sudden clutch
malfunction will indicate the source of the intermittent
fault.
A/C Clutch Diagnosis
This chart should be used for diagnosing the electrical
portion of the A/C compressor clutch circuit. A Tech 2 will
be used in diagnosing the system. The Tech 2 has the
ability to read the A/C request input to the PCM. The Tech
2 can display when the PCM has commanded the A/C
clutch ªON.º The Tech 2 should have the ability to
override the A/C request signal and energize the A/C
compressor relay.
Test Description
IMPORTANT:Do not engage the A/C compressor
clutch with the engine running if an A/C mode is not
selected at the A/C control switch.
The numbers below refer to the step numbers on the
Diagnostic Chart:3. This a test determine is the problem is with the
refrigerant system. If the switch is open, A/C
pressure gauges will be used to determine if the
pressure switch is faulty or if the system is partially
discharged or empty.
4. Although the normal complaint will be the A/C clutch
failing to engage, it is possible for a short circuit to
cause the clutch to run when A/C has not been
selected. This step is a test for that condition.
7. There is an extremely low probability that both relays
will fail at the same time, so the substitution process
is one way to check the A/C Thermostat relay. Use
a known good relay to do a substitution check.
9. The blower system furnishes a ground for the A/C
control circuit, and it also shares a power source
through the Heater and A/C Relay. The blower
must be ªONº in order to test the A/C system.
A/C Clutch Control Circuit Diagnosis
StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Are any other DTCs stored?
Ð
Go to the
other DTC
chart(s) first
Go to Step 3
31. Disconnect the electrical connector at the pressure
switch located on the receiver/drier.
2. Use an ohmmeter to check continuity across the
pressure switch.
Is the pressure switch open?
Ð
Go to Air
Conditioning
to diagnose
the cause of
the open
pressure
switch
Go to Step 4
4IMPORTANT:Before continuing with the diagnosis, the
following conditions must be met:
The intake air temperature must be greater than
15C. (60F).
The engine coolant temperature must be less
than 119C (246F).
1. A/C ªOFF.º
2. Start the engine and idle for 1 minute.
3. Observe the A/C compressor.
Is the A/C compressor clutch engaged even though
A/C has not been requested?
ÐGo to Step 45Go to Step 5
51. Idle the engine.
2. A/C ªONº.
3. Blower ªONº.
4. Observe the A/C compressor.
Is the A/C compressor magnetic clutch engaged?
Ð
Refer to
Diagnostic
Aids
Go to Step 6

Page 1173 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±56
ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
StepNo Ye s Value(s) Action
61. Engine idling.
2. A/C ªONº.
3. Blower ªONº.
4. Observe the ªA/C Requestº d

Page 1174 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±57 ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
StepNo Ye s Value(s) Action
19Replace the A/C switch.
Is the action complete?
ÐVerify repairÐ
20Use an ohmmete

6E±57 ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
StepNo Ye s Value(s) Action
19Replace the A/C switch.
Is the action complete?
ÐVerify repairÐ
20Use an ohmmeter to check continuity between the
electronic A/C thermostat and the blower switch.
Was there an open circuit?
ÐGo to Step 21Go to Step 22
21Repair the open wire (GRN/YEL) between the
thermostat and the blower switch.
Is the action complete?
ÐVerify repairÐ
22Replace the electronic A/C thermostat.
Is the an action complete?
ÐVerify repairÐ
23Check for an open circuit between A/C thermostat relay
and PCM A/C request terminal (E-15).
Was there an open circuit?
ÐGo to Step 24Go to Step 25
24Repair the open circuit between the PCM and A/C
thermostat relay.
Is the action complete?
ÐVerify repairÐ
25Check for an open circuit between the A/C switch (LT
GRN) and the A/C thermostat relay (LT GRN).
Was there an open circuit?
ÐGo to Step 26Go to Step 27
26Repair the open circuit between the A/C switch and the
A/C thermostat relay.
Is the action complete?
ÐVerify repairÐ
271. Ignition ªON.º
2. Use a DVM to check voltage at the A/C pressure
switch (BRN).
Was voltage equal to the specified value?
+BGo to Step 29Go to Step 28
28Repair the open circuit between the 10A A/C fuse and
the pressure switch.
Is the action complete?
ÐVerify repairÐ
29Use an ohmmeter to check continuity between the
pressure switch (GRN/WHT) and the A/C thermostat
relay (GRN/WHT).
Was the circuit open?
ÐGo to Step 30Go to Step 31
30Repair the open circuit between the pressure switch
and the A/C thermostat relay.
Is the action complete?
ÐVerify repairÐ
31Check for damaged pin or terminal at E-15 of the PCM.
Was a damaged pin or terminal found?
ÐGo to Step 32Go to Step 33
32Repair the damaged pin or terminal.
Is the action complete?
ÐVerify repairÐ
33Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?ÐVerify repairÐ

Page 1175 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±58
ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
StepNo Ye s Value(s) Action
341. Remove the A/C compressor relay.
2. Ignition ªON.º
3. Use a DVM to check volt

Page 1176 of 3573

ISUZU TROOPER 1998 Service Repair Manual 6E±59 ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
StepNo Ye s Value(s) Action
451. Remove the A/C compressor relay.
2. Idle the engine.
Is the compressor clutch s

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