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
ProCarManuals.com
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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TEST ACTION APPLICABILITY
12 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?All
Ye s®Go To 13
No®Replace the Ignition Coil.
Perform VERIFICATION TEST VER-5A2.
13 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.
Follow the equipment manufacturer's procedure for pattern analysis.
Is the secondary ignition pattern OK?All
Ye s®Go To 14
No®Repair the indicated component in the Secondary Ignition Sys-
tem.
Perform VERIFICATION TEST VER-5A2.
14 The following are possible causes for mis-fire:
Injector harness connectors, ignition coil circuit, spark plug, mechanical engine
problem, PCM power grounds, irregular cam and crank signal, injectors, restricted
exhaust, intake restriction, PCM, Evap System, EGR System, damaged trigger
wheel, and
accessory drive belts.
Do any of the above causes exist?All
Ye s®Repair as necessary.
Perform VERIFICATION TEST VER-5A2.
No®Go To 15
15The following additional items should be checked as possible mechanical
problems:
ENGINE VACUUM - must be at least 13 inches in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions
ENGINE PCV SYSTEM - must flow freely
ENGINE DRIVE SPROCKETS - must be properly positioned
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - no internal vacuum leaks
FUEL - must be free of contamination
FUEL INJECTOR - plugged or restricted injector; control wire not connected to
correct injector
Are there any engine mechanical problems?All
Ye s®Repair as necessary.
Perform VERIFICATION TEST VER-5A2.
No®Test Complete.
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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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DRIVEABILITY
ProCarManuals.com
TEST ACTION APPLICABILITY
2 At this time the conditions that set this fault are present.
With the DRB, read the FREEZE FRAME DATA 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 monitor.
Is the DRB counting mis-fires at this time?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 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 DATA and SIMILAR CONDITIONS
WINDOW.
With these screens, attempt to duplicate the condition that has set this fault.
While using FREEZE FRAME DATA pay particular attention to the fault setting
conditions, such as speed, temp, load, and map vacuum.
Does the mis-fire reoccur?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 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 of the misfire.
In the FREEZE FRAME, are the adaptive fuel percentages greater than +/- 15
percent?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 5
No®Go To 10
5 With an appropriate container, obtain a fuel sample from the vehicle.
Is the fuel free from contamination?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 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?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 7
No®Relieve fuel pressure and repair as necessary.
Perform VERIFICATION TEST VER-5A2.
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P-0305 CYLINDER #5 MIS-FIRE ÐContinued
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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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DRIVEABILITY
P-0305 CYLINDER #5 MIS-FIRE ÐContinued
ProCarManuals.com
TEST ACTION APPLICABILITY
12 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.
Follow the equipment manufacturer's procedure for pattern analysis.
Is the secondary ignition pattern OK?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 13
No®Repair the indicated component in the Secondary Ignition Sys-
tem.
Perform VERIFICATION TEST VER-5A2.
13 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 ENGINE RPM over 3000 and the operating temp
normal?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®Lab scope cam and crank sensor, check valve timing, running
vacuum test.
Perform VERIFICATION TEST VER-5A2.
No®Go To 14
14The following additional items should be checked as possible mechanical
problems:
ENGINE VACUUM - must be at least 13 inches in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions
ENGINE PCV SYSTEM - must flow freely
ENGINE DRIVE SPROCKETS - must be properly positioned
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - no internal vacuum leaks
FUEL - must be free of contamination
FUEL INJECTOR - plugged or restricted injector; control wire not connected to
correct injector
Are there any engine mechanical problems?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®Repair as necessary.
Perform VERIFICATION TEST VER-5A2.
No®Go To 15
15 The following are other possible causes for mis-fire:
Injector harness connectors, ignition coil circuit, spark plug, mechanical engine
problem, PCM power grounds, irregular cam and crank signal, injectors, restricted
exhaust, intake restriction, PCM, Evap System, EGR System, damaged trigger
wheel, and
accessory drive belts.
Do any of the above causes exist?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®Repair as necessary.
Perform VERIFICATION TEST VER-5A2.
No®Test Complete.
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P-0305 CYLINDER #5 MIS-FIRE ÐContinued
ProCarManuals.com
Symptom:
P-0320 NO CRANK REFERENCE SIGNAL AT PCM
When Monitored and Set Condition:
P-0320 NO CRANK REFERENCE SIGNAL AT PCM
When Monitored: During cranking, with battery voltage between 4.0 volts and 11.6 volts
and manifold vacuum present.
Set Condition: No signal from the crank position sensor is present during engine
cranking or the cam position signal is present with no crank signal.
POSSIBLE CAUSES
CKP SENSOR DEFECTIVE
CRANK POSITION SENSOR GROUND CIRCUIT OPEN
CRANKSHAFT NOTCHES DAMAGED
FLYWHEEL DAMAGED
8-VOLT SUPPLY CIRCUIT OPEN
8-VOLT SUPPLY CIRCUIT SHORT TO GROUND
CKP SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
CMP/CKP SENSOR WIRING HARNESS INTERMITTENT DEFECT
CMP/CKP SENSOR WIRING HARNESS OBSERVABLE DEFECT
CRANK POSITION SENSOR SIGNAL CIRCUIT OPEN
PCM DEFECTIVE
PCM DEFECTIVE (NO CRANK REF SIG)
TEST ACTION APPLICABILITY
1 Cycle the ignition off, then on.
Attempt to start engine.
With the DRB in Input/Output display, read the current CMP and CKP states.
Did the CMP or CKP states change to present while cranking engine?All
Ye s®Go To 2
No®Go To 6
2 Cycle the ignition off, then on.
Attempt to start engine.
With the DRB in Input/Output display, read the current CMP and CKP states.
Did only the CMP state change while cranking engine?All
Ye s®Go To 6
No®Go To 3
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