ISUZU AXIOM 2002 Service Repair Manual

6E±224
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
DTC P0171 ± Fuel Trim System Lean Bank 1

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 P0171 and P0174?
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
loopº.
2. Observe the ªBANK 1 L.T. FUEL TRIMº display on
the Tech 2.
Is the displayed value greater than the specified value?
L.T. Fuel
Trim: +20%
Go to Step 5Go to Step 4
41. Review and record the 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 P0171 while
operating the vehicle to duplicate the Failure
Records conditions.
4. Continue operating the vehicle until the DTC P0171
test runs and note the test result.
Does the Tech 2 indicate DTC P0171 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 P0174 also set?ÐGo to Step 6Go to Step 15
6Visually and physically inspect the vacuum hoses for
disconnections, splits, kinks, improper routing and
improper connections and repair any problem found.
Did your inspection reveal a problem requiring repair?
ÐVerify repairGo 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 repair Go 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 Step11
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 repair Go to Step 11

6E±225
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
DTC P0171 ± Fuel Trim System Lean Bank 1

 
StepNo Ye s Value(s) Action
11Check the fuel for excessive water, alcohol, or other
contaminants (see
Diagnosis in Engine Fuel for the
procedure) and correct the contaminated fuel condition
if present (see
Engine Fuel).
Was the fuel contaminated?
ÐVerify repair Go 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 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 ªFuel System Pressure
Testº and repair fuel system problem if necessary.
Did 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 1 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 Testº, and correct any
problem found (refer to
Fuel Metering System).
Did Injector Balance Test isolate a problem?
ÐVerify repairGo to Step 18
181. Visually and physically inspect the Bank 1 HO2S 1
to ensure that it is installed securely and that the
Bank 1 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±226
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0172 Fuel Trim System Rich Bank 1
060R200054
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a ªclosed loopº
air/fuel metering system is used. While in ªclosed loopº,
the powertrain control module (PCM) monitors the Bank 1
heated oxygen sensors (HO2S) 1 and Bank 2 HO2S 1
signals and adjusts fuel delivery based upon the HO2S
signal voltages. A change made to fuel delivery will be
indicated by the long and short term fuel trim values which
can be monitored with a Tech 2. Ideal fuel trim values are
around 0%; if the HO2S signals are indicating a lean
condition the PCM will add fuel, resulting in fuel trim
values above 0%. If a rich condition is detected, the fuel
trim values will be below 0%, indicating that the PCM is
reducing the amount of fuel delivered. If an excessively
rich condition is detected on Bank 1, the PCM will set DTC
P0172.
The PCM's maximum authority to control long term fuel
trim allows a range between ±15% (automatic
transmission) or ±12 (manual transmission) and +20%.
The PCM's maximum authority to control short term fuel
trim allows a range between ±11% and +20%. The PCM
monitors fuel trim under various engine speed/load fuel
trim cells before determining the status of the fuel trim
diagnostic.
Conditions for Setting the DTC

None of the following was set: EGR DTCs, HO2S
DTCs, (response, transition, open, low volts, no
activity), MAF DTCs, TPS DTCs, MAP DTCs, IATDTCs, canister purge DTCs, EVAP DTCs, injector
circuit DTCs, or misfire DTCs.

Engine coolant temperature is between 6
C (42.8
F)
and 105
C (221
F).

Intake air temperature is between ±40
C (±40
F) and
120
C (248
F).

Manifold absolute pressure is between 24 kPa and 99
kPa.

Throttle angle is steady below 95%.

Vehicle speed is below 136 km/h (85 mph).

Engine speed is between 400 and 6,000 RPM.

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 loopº.

Canister purge duty cycle is greater than 0%, if ªONº.
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

The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.

6E±227
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

A history DTC P0172 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

DTC P0172 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 1 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 oftenthe 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 P0172 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.
DTC P0172 ± Fuel Trim System Rich Bank 1

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 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
loopº.
2. Observe ªB1 Long Term 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 P0172 while
operating the vehicle to duplicate the Failure
Records conditions.
4. Continue operating the vehicle until the DTC P0172
test runs and note test result.
Does the Tech 2 indicate DTC P0172 failed this
ignition?
ÐGo to Step 5
The rich
condition is
not present.
If a
driveability
symptom still
exists, refer
to
Symptoms.
5Is DTC P0175 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 condition requiring repair?
ÐVerify repairGo to Step 8

6E±228
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
DTC P0172 ± Fuel Trim System Rich Bank 1

 
StepNo Ye s Value(s) Action
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. Ignition ªOFFº.
2. Physically inspect the throttle body bore and throttle
plate for coking and foreign objects.
3. If a problem was found, repair as necessary.
Did your inspection reveal a condition requiring repair?
ÐVerify repairGo to Step 11
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
12Ignition ªONº, engine ªOFFº, monitor the TP1 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 8%
Maximum
92%
Go to Step 13Go to Step 21
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 22Go to Step 14
141. Perform ªFuel System Pressure Testº.
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 problem
requiring repair?
ÐVerify repairGo to Step 15
151. Ignition ªONº, engine ªOFFº.
2. Connect a test light between the harness connector
terminals of canister purge solenoid.
Is the test light on?
ÐGo to Step 16Go to Step 19
16Check for short to ground in the wire (YEL/RED)
between the canister purge solenoid and PCM terminal
S-48.
Was there a short to ground?
ÐGo to Step 17Go to Step 18
17Repair the short to ground.
Is the action complete?
ÐVerify repairÐ

6E±229
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
DTC P0172 ± Fuel Trim System Rich Bank 1

 
StepNo Ye s Value(s) Action
18Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
On-Vehicle Service in
Powertrain Control Module and Sensors for
procedures.
And also refer to the latest Service Bulletin.
Check to see if the Latest software is released or not.
And then Down Load the LATEST PROGRAMMED
SOFTWARE to the replacement PCM.
Is the action complete?
ÐVerify repairÐ
191. Perform the ªInjector Balance Testº.
2. If 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 repair Go to Step 20
201. Remove and visually/physically inspect the Bank 1
HO2S 1 for silicon contamination. This will be
indicated by a powdery deposit on the portion of the
HO2S that is exposed to the exhaust stream.
2. If contamination is evident on the Bank 1 HO2S 1,
replace the contaminated sensors.
Did the sensor require replacement?
ÐVerify repair
Refer to
Diagnostic
Aids
211. 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
22Replace the MAF sensor.
Is the action complete?
ÐVerify repairÐ

6E±230
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0174 Fuel Trim System Lean Bank 2
060R200054
Circuit Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a ªclosed loopº
air/fuel metering system is used. While in ªclosed loopº,
the powertrain control module (PCM) monitors the Bank 1
HO2S 1 and Bank 2 HO2S 1 signals and adjusts fuel
delivery based upon the HO2S signal voltages. A change
made to fuel delivery will be indicated by the long and
short term fuel trim values which can be monitored with a
Tech 2. Ideal fuel trim values are around 0%; if the HO2S
signals are indicating a lean condition the PCM will add
fuel, resulting in fuel trim values above 0%. If a rich
condition is detected, the fuel trim values will be below
0%, indicating that the PCM is reducing the amount of fuel
delivered. If an excessively lean condition is detected on
Bank 2, the PCM will set DTC P0174.
The PCM's maximum authority to control long term fuel
trim allows a range between ±15%(automatic
transmission) or ±12%(manual transmission) and +20%.
The PCM monitors fuel trim under various engine
speed/load fuel trim cells before determining the status of
the fuel trim diagnostic.
Conditions for Setting the DTC

None of the following DTCs are set: idle system, EGR,
HO2S, (response, transition, open, low volts, no
activity), MAF, TP sensor, MAP, IAT, canister purge,
EVAP, injector circuit, or misfire.

Engine coolant temperature is between 6
C (42.8
F)
and 105
C (221
F).
Intake air temperature is between ±40
C (±40
F) and
120
C (248
F).

Manifold absolute pressure is between 24 kPa and 99
kPa.

Throttle angle is steady between 3 and 95%.

Vehicle speed is below 136 km/h (85 mph).

Engine speed is between 400 and 6,000 RPM.

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 loopº.

Canister purge duty cycle is greater than 0%, if ªONº.
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

The PCM will turn the MIL ªOFFº on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.

A history DTC P0174 will clear after 40 consecutive
warm-up cycles have occurred without a fault.

DTC P0174 can be cleared by using the Tech 2 ªClear
Infoº function or by disconnecting the PCM battery
feed.

6E±231
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
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 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±232
6VE1 3.5L 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
loopº.
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
disconnections, 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±233
6VE1 3.5L 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 2 S.T. FUEL TRIMº displayed
on the Tech 2.
Does the ªBANK 2 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 Testº 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