Symptom:
P-0171±1/1 FUEL SYSTEM LEAN
When Monitored and Set Condition:
P-0171±1/1 FUEL SYSTEM LEAN
When Monitored: With the engine running in closed loop mode, the ambient, battery
temperature above Ð5 deg. C (20 deg. F) and altitude below 8000 ft.
Set Condition: If the PCM multiplies short term compensation by long term adaptive and
a certain percentage is exceeded for two trips, a freeze frame is stored, the MIL illuminates
and a trouble code is stored.
POSSIBLE CAUSES
FUEL PUMP MODULE DEFECTIVE
TPS VOLTAGE CHANGE NOT SMOOTH
TPS VOLTAGE <0.92V
FUEL INLET STRAINER PLUGGED
ECT SENSOR DEFECTIVE (OUT OF CALIBRATION)
MAP SENSOR DEFECTIVE (OUT OF CALIBRATION)
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR DEFECTIVE (HIGH)
FUEL FILTER/PRESSURE REGULATOR DEFECTIVE (LOW)
FUEL PUMP CAPACITY (VOLUME) OUT OF SPECS
TEST ACTION APPLICABILITY
1 Turn ignition on.
With the DRB, read the DTC's.
Is the Global Good Trip Counter displayed and equal to zero for P0171?All
Ye s®Go To 2
No®Go To 13
2 Ignition On, Engine Not Running
With the DRB, read the TPS voltage.
While monitoring the DRB, slowly open and close the Throttle.
Is the voltage change smooth?All
Ye s®Go To 3
No®Replace the Throttle Position Sensor.
Perform Powertrain Verification Test VER-5A.
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TEST ACTION APPLICABILITY
7 Turn ignition off.
Warning: The fuel system is under a constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
Remove the pressure test port cap at the fuel rail test port. Connect a fuel pressure
gauge to the test port pressure fitting on the fuel rail.
Ignition on. With the DRB, actuate the ASD Fuel System test and observe the fuel
pressure gauge.
Note: Fuel pressure specification is 49.2 psi +/- 5 psi
Choose a conclusion that best matches your fuel pressure reading.All
Below Specification
Go To 8
Within Specification
Go To 11
Above Specification
Replace the fuel filter pressure regulator.
Caution: Stop ALL Actuations.
8 Turn ignition off.
Warning: The fuel system is under a constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
Raise vehicle on hoist,and disconnect the fuel pressure line at the fuel pump module.
Install speial 5/169fuel line adapter tool #6539 between disconnected fuel line and
the fuel pump module.
Attach a fuel pressure test gauge to the88T'' fitting on tool #6539.
Ignition on. With the DRB, actuate the ASD Fuel System test and observe the fuel
pressure gauge.
Note: Fuel pressure specification is 49.2 psi +/- 5 psi.
Is the fuel pressure within specification now?ALL
Ye s®Repair the restriction in the chassis fuel supply line between the
fuel tank and fuel rail.
No®Go to 9
Caution: Stop ALL Actuations.
9Warning: The fuel system is under a constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.
Is the Fuel Inlet Strainer plugged?All
Ye s®Replace the Fuel Inlet Strainer.
No®Go To 10
10 If there are no potential causes remaining, the Fuel Pump Module is assumed to be
defective.
View repair options.All
Repair
Replace the Fuel Pump Module
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P-0171±1/1 FUEL SYSTEM LEAN ÐContinued
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TEST ACTION APPLICABILITY
11 Check for any of the following conditions/mechanical problems.
ENGINE VACUUM Ð must be at least 13 inches in neutral
ENGINE VALVE TIMING Ð must be within specifications
ENGINE COMPRESSION Ð must be within specifications
ENGINE EXHAUST SYSTEM Ð must be free of any restrictions or leaks
ENGINE PVC SYSTEM Ð must flow freely
TORQUE CONVERTER STALL SPEED Ð must be within specifications
POWER BRAKE BOOSTER Ð no internal vacuum leaks
FUEL- must be free of contamination
FUEL INJECTOR Ð plugged or restricted injector; control wire not connected to
correct injector.
Are there any engine mechanical problems?All
Ye s®Repair as necessary.
Perform FUEL SYSTEM/MISFIRE MONITOR VERIFICATION
TEST
No®Go To 12
12 Turn ignition off.
Warning: The fuel system is under constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
Disconnect the fuel supply line at the fuel rail.
Connect fuel line adapter #6539(5/169) or #6631 (3/89) to the disconnected fuel supply
line. Insert the other end of the adapter into a graduated container.
Caution: Do not operate the fuel pump for more than 7 seconds in the next
step. Fuel pump module reservoir may run empty and damage to the fuel
pump may result.
Specification: A good fuel pump will deliver at least 1/4 liter of fuel in 7
seconds.
With the DRB, actuate the ASD Fuel System test for 7 seconds.
Is the fuel pump capacity within specification?All
Ye s®Test Complete.
No®Check for a kinked/damaged fuel supply line between the fuel
tank and fuel rail. If OK, replace the fuel filter/pressure regulator.
Caution: Stop ALL Actuations.
13 The conditions required to set the DTC are no longer present.
With the DRB read and record the freeze frame data and the ªFuel System Similar
Conditions Windowº data.
Utilize the data and try to duplicate the operating conditions at which the DTC was
set. Pay particular attention to the ECT and RPM for added diagnostics.
Note: Refer to any TSB's that may apply to the symptom.
Test Complete
Repair
Test Complete.
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DRIVEABILITY
P-0171±1/1 FUEL SYSTEM LEAN ÐContinued
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TEST ACTION APPLICABILITY
8 Turn ignition off.
Warning: The fuel system is under a constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
Remove the pressure test port cap at the fuel rail test port. Connect a fuel pressure
gauge to the test port pressure fitting on the fuel rail.
Ignition on. With the DRB, actuate the ASD Fuel System test and observe the fuel
pressure gauge.
Note: Fuel pressure specification is 49.2 psi +/þ 5 psi.
Choose a conclusion that best matches your fuel pressure reading.All
Below Specification
Go To 9
Within Specification
Go To 13
Above Specification
Replace the fuel filter/pressure regulator.
Caution: Stop ALL Actuations.
9 Check for any of the following conditions/mechanical problems.
ENGINE VACUUM Ð must be at least 13 inches in neutral
ENGINE VALVE TIMING Ð must be within specifications
ENGINE COMPRESSION Ð must be within specifications
ENGINE EXHAUST SYSTEM Ð must be free of any restrictions or leaks.
ENGINE PVC SYSTEM Ð must flow freely
TORQUE CONVERTER STALL SPEED Ð must be within specifications
POWER BRAKE BOOSTER Ð no internal vacuum leaks
FUEL - must be free of contamination
FUEL INJECTOR Ð plugged or restricted injector; control wire not connected to
correct injector
Are there any engine mechanical problems?All
Ye s®Repair as necessary.
Perform FUEL SYSTEM/MISFIRE MONITOR VERIFICATION
TEST
No®Go To 10
10 Turn ignition off.
Warning: The fuel system is under a constant pressure (even with the engine
off). Before testing or servicing any fuel system hose, fitting or line, the fuel
system pressure must be released.
Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module.
Install special 5/169fuel line adapter tool #6539 between disconnected fuel line and
the fuel pump module.
Attach a fuel pressure test gauge to the ªT'' fitting on tool #6539.
Ignition on. With the DRB, actuate the ASD Fuel System test and observe the fuel
pressure gauge.
Note: Fuel pressure specification is 49.2 psi +/- 5 psi.
Is the fuel pressure within specification now?All
Ye s®Repair the restriction in the chassis fuel supply line between the
fuel tank and fuel rail.
No®Go to 11
Caution: Stop ALL Actuations.
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P0172 -1/1 FUEL SYSTEM RICH ÐContinued
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POSSIBLE CAUSES
OTHER POSSIBLE CAUSES FOR MIS-FIRE
CAM, CRANK, VALVE TIMING, OR VACUUM PROBLEM
ELECTRONIC IGNITION COIL OUTPUT LOW
ENGINE MECHANICAL PROBLEM
SECONDARY IGNITION PATTERN IRREGULAR
FUEL CONTAMINATION
FUEL PRESSURE LEAK DOWN OUT OF SPECIFICATION
FUEL PUMP AMPERAGE OUT OF SPECIFICATION
FUEL PUMP CAPACITY OUT OF SPECIFICATION
FUEL PUMP PRESSURE OUT OF SPECIFICATION
MIS-FIRE DOES NOT REOCCUR
TEST ACTION APPLICABILITY
1 With the DRB, read the DTCs.
Is the MIS-FIRE GOOD TRIP counter displayed and equal to zero?All
Ye s®Go To 2
No®Go To 3
2 At this time the conditions that set this fault are present.
With the DRB, read the FREEZE FRAME and SIMILAR CONDITIONS WINDOWS.
Attempt to operate the vehicle in the similar conditions.
When the vehicle is operating in the SIMILAR CONDITIONS WINDOW, go to the
WHICH CYLINDER IS MISFIRING screen.
Is the DRB counting mis-fires at this time?All
Ye s®Go To 4
No®Go To 3
3 At this time the mis-fire does not exist or is an intermittent problem.
With the DRB, read the FREEZE FRAME and SIMILAR CONDITIONS WINDOW.
With these screens, attempt to duplicate the condition that has set this fault.
While using FREEZE FRAME pay particular attention to the fault setting condi-
tions, such as speed, temp, load, and map vacuum.
Does the mis-fire reoccur?All
Ye s®Go To 4
No®Mis-fire no longer exists.
Perform VERIFICATION TEST VER-5A2.
4 With the DRB, read the FREEZE FRAME DATA.
Use the freeze frame data and attempt to determine the cause.
In the FREEZE FRAME, are the adaptive fuel percentages greater than +/- 15%?All
Ye s®Go To 5
No®Go To 10
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P-0300 MULTIPLE CYLINDER MIS-FIRE ÐContinued
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TEST ACTION APPLICABILITY
5 With an appropriate container, obtain a fuel sample from the vehicle.
Is the fuel free from contamination?All
Ye s®Go To 6
No®Replace contaminated fuel and clean system.
Perform VERIFICATION TEST VER-5A2.
6 Perform Fuel Pressure Leak Down Test per service instructions.
Did the Fuel Pressure Leak Down Test pass?All
Ye s®Go To 7
No®Relieve fuel pressure and repair as necessary.
Perform VERIFICATION TEST VER-5A2.
7 Perform Fuel Pump Amperage Test per service instructions.
Did the Fuel Pump Amperage Test pass?All
Ye s®Go To 8
No®Relieve fuel pressure and repair as necessary.
Perform VERIFICATION TEST VER-5A2.
8 Perform Fuel Pump Capacity Test per service instructions.
Did the Fuel Pump Capacity Test pass?All
Ye s®Go To 9
No®Relieve fuel pressure and repair as necessary.
Perform VERIFICATION TEST VER-5A2.
9 Perform Fuel Pump Pressure Test per service instructions.
Did the Fuel Pump Pressure Test pass?All
Ye s®Go To 10
No®Relieve fuel pressure and repair as necessary.
Perform VERIFICATION TEST VER-5A2.
10 With the DRB, read the FREEZE FRAME DATA.
Use the freeze frame data and attempt to determine the cause.
In the FREEZE FRAME, is the LOAD VALUE over 50% and the temp normal
operating temp normal?All
Ye s®Go To 12
No®Go To 11
11 With the DRB, read the FREEZE FRAME window.
Use the freeze frame data and attempt to determine the cause.
In the FREEZE FRAME, is the ENGINE RPM over 3000 and the operating temp
normal?All
Ye s®Lab scope cam and crank sensor, check valve timing, running
vacuum test.
Perform VERIFICATION TEST VER-5A2.
No®Go To 14
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P-0300 MULTIPLE CYLINDER MIS-FIRE ÐContinued
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Symptom List:
P-0305 CYLINDER #5 MIS-FIRE
P-0306 CYLINDER #6 MIS-FIRE
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be P-0305 CYLINDER #5 MIS-FIRE.
When Monitored and Set Condition:
P-0305 CYLINDER #5 MIS-FIRE
When Monitored: With the engine running, after successfully performing Crank Sensor
learn.
Set Condition: When more than a 2% misfire rate is measured during two trips, or with
a 10% to 30% misfire rate during one trip.
P-0306 CYLINDER #6 MIS-FIRE
When Monitored: With the engine running, after successfully performing Crank Sensor
learn.
Set Condition: When more than a 2% misfire rate is measured during two trips, or with
a 10% to 30% misfire rate during one trip.
POSSIBLE CAUSES
OTHER POSSIBLE CAUSES FOR MIS-FIRE
CAM, CRANK, VALVE TIMING, OR VACUUM PROBLEM
ELECTRONIC IGNITION COIL OUTPUT LOW
ENGINE MECHANICAL PROBLEM
SECONDARY IGNITION PATTERN IRREGULAR
FUEL CONTAMINATION
FUEL PRESSURE LEAK DOWN OUT OF SPECIFICATION
FUEL PUMP AMPERAGE OUT OF SPECIFICATION
FUEL PUMP CAPACITY OUT OF SPECIFICATION
FUEL PUMP PRESSURE OUT OF SPECIFICATION
MIS-FIRE DOES NOT REOCCUR
TEST ACTION APPLICABILITY
1 With the DRB, read the DTCs.
Is the MIS-FIRE GOOD TRIP counter displayed and equal to zero?ENGINE - 3.0L V6
and/or ENGINE -
3.3L V6 and/or EN-
GINE - 3.8L V6
and/or ENGINE -
3.3L V6 FFV Ye s®Go To 2
No®Go To 3
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TEST ACTION APPLICABILITY
7 Perform Fuel Pump Amperage Test per service instructions.
Did the Fuel Pump Amperage Test pass?ENGINE - 3.0L V6
and/or ENGINE -
3.3L V6 and/or EN-
GINE - 3.8L V6
and/or ENGINE -
3.3L V6 FFV
Ye s®Go To 8
No®Relieve fuel pressure and repair as necessary.
Perform VERIFICATION TEST VER-5A2.
8 Perform Fuel Pump Capacity Test per service instructions.
Did the Fuel Pump Capacity Test pass?ENGINE - 3.0L V6
and/or ENGINE -
3.3L V6 and/or EN-
GINE - 3.8L V6
and/or ENGINE -
3.3L V6 FFV
Ye s®Go To 9
No®Relieve fuel pressure and repair as necessary.
Perform VERIFICATION TEST VER-5A2.
9 Perform Fuel Pump Pressure Test per service instructions.
Did the Fuel Pump Pressure Test pass?ENGINE - 3.0L V6
and/or ENGINE -
3.3L V6 and/or EN-
GINE - 3.8L V6
and/or ENGINE -
3.3L V6 FFV
Ye s®Go To 10
No®Relieve fuel pressure and repair as necessary.
Perform VERIFICATION TEST VER-5A2.
10 With the DRB, read the FREEZE FRAME DATA.
Use the freeze frame data and attempt to determine the cause of the misfire.
In the FREEZE FRAME, is the LOAD VALUE over 50% and the temp normal
operating temp?ENGINE - 3.0L V6
and/or ENGINE -
3.3L V6 and/or EN-
GINE - 3.8L V6
and/or ENGINE -
3.3L V6 FFV
Ye s®Go To 11
No®Go To 13
11 Engine Off.
Connect a suitable engine analyzer to the engine.
Allow the Engine to idle.
NOTE: If the Engine will not idle, maintain a constant RPM above idle.
NOTE: Set the scope to read display or parade pattern.
Remove any spark plug wire.
Observe the Secondary KV Line.
Is the open secondary voltage at least 25 KV?ENGINE - 3.0L V6
and/or ENGINE -
3.3L V6 and/or EN-
GINE - 3.8L V6
and/or ENGINE -
3.3L V6 FFV
Ye s®Go To 12
No®Replace the Electonic Ignition Coil.
Perform VERIFICATION TEST VER-5A2.
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P-0305 CYLINDER #5 MIS-FIRE ÐContinued
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