check engine ISUZU TROOPER 1998 Service Repair Manual

6E±163 ENGINE DRIVEABILITY AND EMISSIONS

Ignition voltage is above 9.5 volts.

Fuel system is in ªclosed loop.º
Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
failure 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 P0174 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, observe theBank 2 HO2S 1 display on the Tech 2 while moving
connectors and wiring harnesses related to the engine
harness. A change in the display will indicate the
location of the fault.
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.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. DTCs other than P0171 and P0174 may indicate a
condition present which may cause a lean condition.
If this is the case, repairing the condition which
caused the other DTC will most likely correct the
DTC P0171/P0174.
4. If the DTC P0174 test passes while the Failure
Records conditions are being duplicated, the lean
condition is intermittent. Refer to
Diagnostic Aids or
Symptoms for additional information on diagnosing
intermittent problems.

6E±164
ENGINE DRIVEABILITY AND EMISSIONS
DTC P0174 ± Fuel Trim System Lean Bank 2

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Are any DTCs set other than P0174 and P0171?
Ð
Go to the
applicable
DTC charts
and repair the
other DTCs
before
proceeding
with this
chart.
Go to Step 3
31. Start the engine and operate the vehicle in ªclosed
loop.º
2. Observe the ªBANK 2 L.T. FUEL TRIMº display on
the Tech 2.
Is the displayed values greater than the specified
values?
L.T. Fuel
Trim: +20%
Go to Step 5Go to Step 4
41. Review and record Tech 2 Failure Records data.
2. Clear the DTC P0171/P0174 and operate the
vehicle to duplicate the Failure Records conditions.
3. Monitor the Tech 2 ªDTCº info for DTC P0174 while
operating the vehicle to duplicate the Failure
Records conditions.
4. Continue operating the vehicle until the DTC P0174
test runs.
5. Note the test result.
Does the Tech 2 indicate DTC P0174 failed this
ignition?
ÐGo to Step 5
The lean
condition is
not present.
If a
driveability
symptom still
exists, refer
to
Symptoms
section.
5Was DTC P0171 also set?ÐGo to Step 6Go to Step 15
6Visually and physically inspect the vacuum hoses for
disconnects, splits, kinks, improper routing and
improper connections and repair any problem found.
Did your inspection reveal a problem requiring repair?
ÐVerify repair Go to Step 7
7Visually and physically inspect the crankcase
ventilation valve for proper installation and repair any
problem found (refer to
Crankcase Ventilation
System
).
Did your inspection reveal a problem requiring repair?
ÐVerify repairGo to Step 8
81. Inspect the MAF sensor inlet screen for damage or
for the presence of foreign objects which may
partially block the air flow sample through the MAF
sensor.
2. Correct any problem that is found as necessary.
Did your inspection of the MAF sensor reveal a
condition requiring repair?
ÐVerify repairGo to Step 9
9Start the engine and note the idle quality.
Is a high or unsteady idle being experienced?
ÐGo to Step 10Go to Step 11

6E±165 ENGINE DRIVEABILITY AND EMISSIONS
DTC P0174 ± Fuel Trim System Lean Bank 2

 
StepNo Ye s Value(s) Action
101. Visually and physically inspect the throttle body,
intake manifold, EGR valve and the EGR feed pipe
for vacuum leaks.
2. Repair any vacuum leaks as necessary.
Did your inspection reveal a vacuum leak?
ÐVerify repairGo to Step 11
11Check the fuel for excessive water, alcohol, or other
contaminants (see
Diagnosis in Engine Fuel for
procedure) and correct the contaminated fuel condition
is present (see
Engine Fuel).
Was the fuel contaminated?
ÐVerify repairGo to Step 12
121. Visually and physically inspect the PCM injector
grounds, power grounds and sensor grounds to
ensure that they are clean, tight, and in their proper
locations.
2. If a faulty ground condition is present, correct it as
necessary.
Did your inspection reveal a condition requiring repair?
ÐVerify repairGo to Step 13
131. Disconnect the MAF sensor electrical connector.
2. Operate the vehicle in ªclosed loopº while
monitoring the ªBANK 1 S.T. FUEL TRIMº displayed
on the Tech 2.
Does the ªBANK 1 S.T. FUEL TRIMº value decrease to
near the specified value?
0%Go to Step 19Go to Step 14
14Perform the procedure in the ºFuel System Pressure
Testº and repair fuel system problem if necessary.
Did the Fuel System Pressure Test isolate a condition
requiring repair?
ÐVerify repairGo to Step 15
151. Visually and physically inspect the intake manifold,
injector O-rings, EGR adapter, EGR valve and the
EGR feed pipes for vacuum leaks.
2. Repair any problem that is found.
Did your inspection reveal a problem?
ÐVerify repairGo to Step 16
16Visually and physically inspect the Bank 2 exhaust
manifold for leaks and loose or missing hardware and
correct any problem found.
Did your inspection reveal a problem?
ÐVerify repairGo to Step 17
17Perform the ªInjector Balance Test,º and correct any
problem found (refer to
Fuel Metering System).
Did the Injector Balance Test isolate a problem?
ÐVerify repair Go to Step 18
181. Visually and physically inspect the Bank 2 HO2S 1
to ensure that it is installed securely and that the
Bank 2 HO2S 1 pigtail and wiring harness are not
contacting the exhaust or otherwise damaged.
2. If a problem is found, correct it as necessary.
Did your inspection reveal a problem?
ÐVerify repair
Refer to
Diagnostic
Aids
19Replace the MAF sensor.
Is the action complete?
ÐVerify repairÐ

6E±167 ENGINE DRIVEABILITY AND EMISSIONS

Barometric pressure is greater than 72.5 kPa.

Mass air flow is between 2 g/second and 200 g/second.

Ignition voltage is above 9.5 volts.

Fuel system is in ªclosed loop.º
Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
failure 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 P0175 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, observe the
Bank 2 HO2S 1 display on the Tech 2 while moving
connectors and wiring harnesses related to the engine
harness. A change in the display will indicate the
location of the fault.
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.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. DTCs other than P0172 and P0175 may indicate a
condition present which may cause a lean condition.
If this is the case, repairing the condition which
caused the other DTC will most likely correct the
DTC P0172/P0175.
4. If the DTC P0175 test passes while the Failure
Records conditions are being duplicated, the rich
condition is intermittent. Refer to
Diagnostic Aids or
Symptoms for additional information on diagnosing
intermittent problems.

6E±168
ENGINE DRIVEABILITY AND EMISSIONS
DTC P0175 ± Fuel Trim System Rich Bank 2

StepActionValue(s)Ye sNo
1Was the ºOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Are any DTCs set other than P0172 and P0175?
Ð
Go to the
applicable
DTC charts
and repair the
other DTCs
before
proceeding
with this
chart.
Go to Step 3
31. Start the engine and operate the vehicle in ªclosed
loop.º
2. Observe the ªBANK 2 L.T. FUEL TRIMº display on
the Tech 2.
Is the displayed value more negative than the specified
value?
L.T. Fuel
Trim: ±15%
(auto. trans.)
OR ±12%
(man. trans.)
Go to Step 5Go to Step 4
41. Review and record the Tech 2 Failure Records data.
2. Clear the DTC P0172/P0175 and operate the
vehicle to duplicate the Failure Records conditions.
3. Monitor the Tech 2 ªDTCº info for DTC P0175 while
operating the vehicle to duplicate the Failure
Records conditions.
4. Continue operating the vehicle until the DTC P0175
test runs.
5. Note the test result.
Does the Tech 2 indicate DTC P0175 failed this
ignition?
ÐGo to Step 5
The rich
condition is
not present.
If a
driveability
symptom still
exists, refer
to
Symptoms.
5Was DTC P0172 also set?ÐGo to Step 6Go to Step 15
6Visually and physically inspect the air filter element and
replace it if necessary.
Did the air filter require replacement?
ÐVerify repairGo to Step 7
7Visually and physically inspect the air intake duct for
collapse or restriction and repair if necessary.
Did your inspection reveal a problem requiring repair?
ÐVerify repairGo to Step 8
8Inspect the MAF sensor inlet screen for damage or for
the presence of foreign objects which may partially
block air flow through the screen and correct any
problem found.
Did your inspection of the MAF sensor reveal a
condition requiring repair or replacement?
ÐVerify repairGo to Step 9
9Start the engine and note the idle quality.
Is a low or unsteady idle being experienced?
ÐGo to Step 10Go to Step 11
101. Turn the ignition off and physically inspect the
throttle body bore, throttle plate, and IAC passages
for coking and foreign objects.
2. If a problem was found, repair as necessary.
Did your inspection reveal a condition requiring repair?
ÐVerify repairGo to Step 11

6E±169 ENGINE DRIVEABILITY AND EMISSIONS
DTC P0175 ± Fuel Trim System Rich Bank 2

 
StepNo Ye s Value(s) Action
111. Disconnect the vacuum hose from the fuel pressure
regulator and inspect the hose for the presence of
fuel.
2. If fuel is present in the vacuum hose, replace the
fuel pressure regulator (refer to
Fuel Metering
System
).
Did the fuel pressure regulator require replacement?
ÐVerify repairGo to Step 12
121. Ignition ªON,º engine ªOFF.º
2. Monitor the TP Angle display on the Tech 2 while
slowly depressing the accelerator pedal.
Does the TP Angle display increase steadily and
evenly from minimum value at closed throttle to
maximum value at wide-open throttle?
Minimum 0%
Maximum
100%
Go to Step 13Go to Step 18
131. Disconnect the MAF sensor electrical connector.
2. Operate the vehicle in ªclosed loopº while
monitoring the ªBANK 1 L.T. FUEL TRIMº and
ªBANK 1 S.T. FUEL TRIMº display on the Tech 2.
Did both values change to near the specified value?
0%Go to Step 19Go to Step 14
141. Perform the ªFuel System Pressure Test.º
2. If Fuel System Pressure Test isolates a problem,
repair as necessary (refer to
Engine Fuel or Fuel
Metering System
).
Did the Fuel System Pressure Test isolate a condition
requiring repair?
ÐVerify repairGo to Step 16
15Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?ÐVerify repairÐ
161. Perform the ªInjector Balance Test.º
2. If the Injector Balance Test isolates a problem,
repair as necessary (refer to
Fuel Metering
System
).
Did the Injector Balance Test isolate a problem
requiring repair?
ÐVerify repairGo to Step 17
171. Remove and visually/physically inspect the Bank 2
HO2S 1 for silicon contamination. This will be
indicated by a powdery white deposit on the portion
of the HO2S that is exposed to the exhaust stream.
2. If contamination is evident on the Bank 2 HO2S 1,
replace the contaminated sensor.
Did the sensor require replacement?
ÐVerify repair
Refer to
Diagnostic
Aids
181. Check the TP sensor mounting screws and tighten
or replace them as necessary if they are loose or
missing.
2. If the screws are OK, replace the TP sensor.
Is the action complete?
ÐVerify repairÐ
19Replace the MAF sensor.
Is the action complete?
ÐVerify repairÐ

6E±170
ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0201 Injector 1 Control Circuit
D06RW034
Circuit Description
The powertrain control module (PCM) has six individual
injector driver circuits. Each controls an injector. When a
driver circuit is grounded by the PCM, the injector is
activated. The PCM monitors the current in each driver
circuit. The voltage on each driver is monitored to detect
a fault. If the voltage is not what the PCM expects to
monitor on the circuit, a DTC is set. This DTC is also set if
an injector driver is shorted to voltage or if there is an open
circuit.
Conditions for Setting the DTC

The battery voltage is more than 9 volts.

The engine is turning, determined by 58X crankshaft
position input signal.

The injector voltage does not equal the ignition voltage
when the injector is commanded ªOFFº or the injector
voltage does not equal 0 volts when the injector is
commanded ªON.º

The above conditions are met for 15 seconds.
Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp
(MIL) 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.
Conditions for Clearing the MIL/DTC

DTC P0201 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
An injector driver circuit that is open or shorted to voltage
will cause a DTC P0201 to set. It will also cause a misfire
due to an inoperative injector. A misfire DTC will also be
set indicating which cylinder is inoperative.
Long term and short term fuel trims that are excessively
high or low are a good indication that an injector is faulty.
Use Fuel Injector Coil Test Procedure to check for faulty
injectors.
Test Description
The number(s) below refer to the step number(s) on the
Diagnostic Chart.
3. This step determines if DTC P0201 is the result of a
hard failure or an intermittent condition.
5. A special injector test connector is provided so that
the injectors can be electrically tested without
removal of the manifold. On the Trooper, the
special 7-way gray connector is located at the front
of the charcoal canister. The test connector can be
identified by the blue connector lock which is
tethered to the wiring harness. If the light for
cylinder 1 is ªONº steady before cranking the engine
as well as while cranking the engine, then the
injector driver circuit is shorted to ground.

6E±171 ENGINE DRIVEABILITY AND EMISSIONS
If the test light blinks while cranking, the PCM and
the wiring to the injectors are OK. The Fuel Injector
Coil Test Procedure will check if the injectors are
faulty.
R321054
7. Because the test light was ªONº steady, voltage to
the injector is OK, but the driver circuit is grounded
at all times. This step determines if the circuit is
shorted to ground or the PCM is faulty.
9. The reading should be about 12-14
.
10.Locating the open in the harness or in the injector
will require removal of the manifold to provide
access.
DTC P0201 ± Injector 1 Control Circuit

StepActionValue(s)Ye sNo
1Was the ªOn-Board Diagnostic (OBD) System Checkº
performed?
ÐGo to Step 2
Go to OBD
System
Check
2Will the engine start?
ÐGo to Step 3
Go to Engine
Cranks But
Will Not Run
chart
31. Install the Tech 2. Clear the DTC.
2. Idle the engine for one minute.
Does DTC P0201 reset?
ÐGo to Step 5Go to Step 4
41. Review the Freeze Frame data with the ignition
ªONº and the engine ªOFFº and note the
parameters.
2. Operate the vehicle within the Freeze Frame
conditions as noted.
Does P0201 reset?
ÐGo to Step 5
Go to
Diagnostic
Aids
51. Engine ªOFF.º
2. Disconnect the injector connector.
3. Install an injector test light 5-8840-2636-0 on the
injector test connector.
4. Crank the engine and note the light.
Does the injector test light blink?
Ð
Go to Fuel
Injector Coil
Test
Procedure
Go to Step 6
6Note whether the injector test light for cylinder 1 was
ªOFFº or ªONº steady in step 5.
Was the test light ªONº steady while cranking the
engine?
ÐGo to Step 7Go to Step 9

6E±172
ENGINE DRIVEABILITY AND EMISSIONS
DTC P0201 ± Injector 1 Control Circuit

 
StepNo Ye s Value(s) Action
71. Disconnect the PCM connector for the affected
injectors.
2. With a test light connected to B+, probe the affected
injector driver circuit.
Does the test light illuminate?
ÐGo to Step 8Go to Step 15
8Repair short to ground in the injector driver circuit.
Is the action complete?
Ð
Go to OBD
System
Check
Ð
91. Disconnect the injector test connector.
2. At the injector side of the harness, connect an
ohmmeter between the positive wire (red with blue
tracer) and the wire for cylinder 1 (green with white
tracer).
Does the ohmmeter indicate continuity?
ÐGo to Step 11Go to Step 10
10Repair the open injector harness wire or open injector.
Is the action complete?
ÐVerify repairÐ
11At the PCM side of the injector test connector, check
the green/white wire for a short to voltage.
Was there a short to voltage?
ÐGo to Step 12Go to Step 13
12Repair the short to voltage.
Is the action complete?
ÐVerify repairÐ
13Check for an open circuit between the injector test
connector and the PCM.
Was there an open circuit?
ÐGo to Step 14Go to Step 15
14Repair the open circuit.
Is the action complete?
ÐVerify repairÐ
15Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
UBS 98model year Immobilizer
Workshop Manual.
Is the action complete?ÐVerify repairÐ

6E±173 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0202 Injector 2 Control Circuit
D06RW034
Circuit Description
The powertrain control module (PCM) has six individual
injector driver circuits. Each controls an injector. When a
driver circuit is grounded by the PCM, the injector is
activated. The PCM monitors the current in each driver
circuit. The voltage on each driver is monitored to detect
a fault. If the voltage is not what the PCM expects to
monitor on the circuit, a DTC is set. This DTC is also set if
an injector driver is shorted to voltage or if there is an open
circuit.
Conditions for Setting the DTC

The battery voltage is more than 9 volts.

The engine is turning, determined by 58X crankshaft
position input signal.

The injector voltage does not equal the ignition voltage
when the injector is commanded ªOFFº or the injector
voltage does not equal 0 volts when the injector is
commanded ªON.º

The above conditions are met for 15 seconds.
Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp
(MIL) 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.
Conditions for Clearing the MIL/DTC

DTC P0202 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.
Diagnostic Aids
An injector driver circuit that is open or shorted to voltage
will cause a DTC P0202 to set. It will also cause a misfire
due to an inoperative injector. A misfire DTC will also be
set indicating which cylinder is inoperative.
Long term and short term fuel trims that are excessively
high or low are a good indication that an injector is faulty.
Use Fuel Injector Coil Test Procedure to check for faulty
injectors.
Test Description
The number(s) below refer to the step number(s) on the
Diagnostic Chart.
3. This step determines if DTC P0202 is the result of a
hard failure or an intermittent condition.
5. A special injector test connector is provided so that
the injectors can be electrically tested without
removal of the manifold. On the Trooper, the
special 7-way gray connector is located at the front
of the charcoal canister. The test connector can be
identified by the blue connector lock which is
tethered to the wiring harness. If the light for
cylinder 2 is ªONº steady before cranking the engine
as well as while cranking the engine, then the
injector driver circuit is shorted to ground.