Theory of Operation
The fuel feedback system will maintain a stoiciometric fuel/air mixture,14.7:1, by modifying the injector pulsewidth
according to the oxygen content of the exhaust gas. The PCM makes short termand long term fuel corrections to
maintain stoiciometric fuel/air ratio for best catalytic converter efficiency. Short term fuel correction is based on
upstream O2 sensor output and is designed for quick engine response. The long term fuel correction compensated
for variations in the engine specifications, sensor tolerances and component aging and is designed to correct rich
and lean conditions over a longer period of time.
When Monitored:
With the engine running in closed loop mode, the ambient/battery temperature above 20 deg. F and altitude
below 8500 ft.
Set Condition:
If the PCM multiplies short term compensation by long term adaptive and a purge fuel multiplier and the result
is below a certain value for 30 seconds over two trips, a freeze frame is stored, the MIL illuminates and a
trouble code is stored. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes
O2 SENSOR
(K41) O2 SENSOR 1/1 SIGNAL CIRCUIT OPEN
(K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO VOLTAGE
1/1 O2 SENSOR HEATER OPERATION
EVAP SYSTEM OPERATION
TP SENSOR VOLTAGE GREATER THAN 0.92 OF A VOLT WITH THROTTLE CLOSED
TP SENSOR
FUEL FILTER/PRESSURE REGULATOR
MAP SENSOR
ECT SENSOR
ENGINE MECHANICAL CONDITION
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.GOOD TRIP EQUAL TO ZERO
NOTE: Check for contaminates that may have damaged the O2 Sensor: contaminated fuel, unapproved sil-
icone, oil and coolant.
Ignition on, engine not running.
With the scan tool, read DTCs and record the related Freeze Frame data.
NOTE: Any O2 Sensor, TPS, ECT, MAP, or EVAP DTCs must be repaired before continuing.
Is the Good Trip Counter displayed and equal to zero?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITIONSymptom (Diagnostic Procedure).
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Theory of Operation
The fuel feedback system will maintain a stoiciometric fuel/air mixture,14.7:1, by modifying the injector pulsewidth
according to the oxygen content of the exhaust gas. The PCM makes short termand long term fuel corrections to
maintain stoiciometric fuel/air ratio for best catalytic converter efficiency. Short term fuel correction is based on
upstream O2 sensor output and is designed for quick engine response. The long term fuel correction compensated
for variations in the engine specifications, sensor tolerances and component aging and is designed to correct rich
and lean conditions over a longer period of time.
When Monitored:
With the engine running in closed loop mode, the ambient/battery temperature above 20 deg. F and altitude
below 8500 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. Two Trip Fault. Three good
trips to turn off the MIL.
Possible Causes
FUEL PRESSURE OUT OF SPECS
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SENSOR
(K43) O2 SENSOR 2/1 SIGNAL CIRCUIT SHORTED TO GROUND
O2 SENSOR 2/1 HEATER OPERATION
TP SENSOR
MAP SENSOR
ECT SENSOR
ENGINE MECHANICAL CONDITION
FUEL FILTER/PRESSURE REGULATOR
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.GOOD TRIP EQUAL TO ZERO
NOTE: Check for contaminates that may have damaged the O2 Sensor: contaminated fuel, unapproved sil-
icone, oil and coolant.
Ignition on, engine not running.
With the scan tool, read DTCs and record the related Freeze Frame data.
Is the Good Trip Counter displayed and equal to zero?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
Theory of Operation
The fuel feedback system will maintain a stoiciometric fuel/air mixture,14.7:1, by modifying the injector pulsewidth
according to the oxygen content of the exhaust gas. The PCM makes short termand long term fuel corrections to
maintain stoiciometric fuel/air ratio for best catalytic converter efficiency. Short term fuel correction is based on
upstream O2 sensor output and is designed for quick engine response. The long term fuel correction compensated
for variations in the engine specifications, sensor tolerances and component aging and is designed to correct rich
and lean conditions over a longer period of time.
When Monitored:
With the engine running in closed loop mode, the ambient/battery temperature above 20 deg. F and altitude
below 8500 ft.
Set Condition:
If the PCM multiplies short term compensation by long term adaptive and a purge fuel multiplier and the result
is below a certain value for 30 seconds over two trips, a freeze frame is stored, the MIL illuminates and a
trouble code is stored. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes
O2 SENSOR
(K43) O2 SENSOR 2/1 SIGNAL CIRCUIT OPEN
(K43) O2 SENSOR 2/1 SIGNAL CIRCUIT SHORTED TO VOLTAGE
2/1 O2 SENSOR HEATER OPERATION
EVAP SYSTEM OPERATION
TP SENSOR VOLTAGE GREATER THAN 0.92 OF A VOLT WITH THROTTLE CLOSED
TP SENSOR
FUEL FILTER/PRESSURE REGULATOR
MAP SENSOR
ECT SENSOR
ENGINE MECHANICAL CONDITION
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.GOOD TRIP EQUAL TO ZERO
NOTE: Check for contaminates that may have damaged the O2 Sensor: contaminated fuel, unapproved sil-
icone, oil and coolant.
Ignition on, engine not running.
With the scan tool, read DTCs and record the related Freeze Frame data.
NOTE: Any O2 Sensor, TPS, ECT, MAP, or EVAP DTCs must be repaired before continuing.
Is the Good Trip Counter displayed and equal to zero?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITIONSymptom (Diagnostic Procedure).
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
4.(G127) EOT SENSOR SIGNAL CIRCUIT SHORTED TO (Z1) GROUND CIRCUIT
Measure the resistance between the (G127) Engine Oil Temp Sensor
Signal circuit and the (Z1) ground circuit at the EOT Sensor harness
connector.
Istheresistancebelow100ohms?
Ye s>>
Repair the short between the (Z1) ground circuit and the
(G127) Engine Oil Temp Sensor Signal circuit.
Perform POWERTRAIN VERIFICATION TEST. (Refer to 9 -
ENGINE - STANDARD PROCEDURE)
No>>
Go To 5
5.PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.
If there are no possible causes remaining, view repair.
Repair
Replace and program the Powertrain Control Module per Service Information.
Perform POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
P0300-MULTIPLE CYLINDER MISFIRE
For a complete wiring diagramRefer to Section 8W.
When Monitored:
Any time the engine is running, and the adaptive numerator has been successfully updated.
Set Condition:
When more than a 2% (2.5% LEV) misfire rate is measured during two trips. Above 3000 RPM 1 trip less than
3000 RPM 2 trip. Three good trips to turn off the MIL.
Possible Causes
(K342) ASD RELAY OUTPUT CIRCUIT
INJECTOR CONTROL CIRCUIT
COIL CONTROL CIRCUIT
IGNITION WIRE
SPARK PLUG
IGNITION COIL
FUEL PUMP INLET STRAINER PLUGGED
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP MODULE
FUEL PRESSURE LEAK DOWN
FUEL INJECTOR
ENGINE MECHANICAL
PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.CYLINDER MIS-FIRE CONDITION ACTIVE
NOTE: Check for any TSB’s that apply to a Misfire condition. Review the vehicle repair history for any mis-
fire condition repairs that have been performed.
Star the engine.
Observe the WHICH CYLINDER IS MISFIRING screen for at least one minute on the scan tool.
Is there a misfire present?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2.VISUAL INSPECTION
NOTE: Anything that affects the speed of the crankshaft can cause a misfireDTC.
NOTE: When a Misfire is detected for a particular cylinder, the PCM will shut down that cylinders Injector
Control circuit.
- Visually inspect the engine for any of the following conditions.
- Worn serpentine belt
- Binding Engine-Driven accessories: A/C Compressor, P/S Pump, Water pump.
- Misalignment of the Water pump, P/S Pump and A/C Compressor pulleys
- Corroded PCM power and ground circuits.
- Improper CKP, CMP, MAP, and TP Sensor mounting
- Poor connector/terminal to component connection. i.e., CKP sensor, Fuel Injector, Ign coil, etc.
14.IGNITION WIRE
NOTE: If the vehicle being tested does not have an ignition wire answer YES to this test and continue.
Turn the ignition off.
Remove the ignition wire.
Measure the resistance of the ignition wire.
Is the resistance below 10K ohms?
Ye s>>
Go To 14
No>>
Replace the Ignition Wire.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
15.IGNITION COIL
Disconnect the Ignition Coil harness connector.
RemovetheFuelPumpfuseorASDfuse.
Using a 12-volt test light connected to 12-volts, probe the Ignition Coil Control circuit.
Crank the engine for 5 seconds while observing the test light.
Does the test light brightly blink/flicker?
Ye s>>
Replace the Ignition Coil.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 15
16.COIL CONTROL CIRCUIT
Turn the ignition off.
Disconnect the Ignition Coil harness connector.
Disconnect the PCM harness connectors.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage
the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool 8815 to perform
diagnosis.
Check the Coil Control circuit for an open, short to ground, and short to voltage.
Was a problem found with the Coil Control circuit?
Ye s>>
Repair the Coil Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 17
17.PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.
Were there any problems found?
Ye s>>
Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
15.IGNITION COIL
Disconnect the Ignition Coil harness connector.
Remove the Fuel Pump Relay.
Using a 12-volt test light connected to 12-volts, probe the (K19) Ignition
Coil Control No.1 circuit.
Crank the engine for 5 seconds while observing the test light.
NOTE: The primary resistance of the 8.3L Ignition coil is 0.53 to
0.65 of an ohm at 77°F (25°C).
Does the test light brightly blink/flicker?
Ye s>>
Replace the Ignition Coil.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 16
16.(K19) IGNITION COIL CONTROL NO.1 CIRCUIT
Turn the ignition off.
Disconnect the C1 PCM harness connector.
Check the (K19) Ignition Coil Control No.1 circuit for an open or short to
ground.
Was a problem found with the Coil Control circuit?
Ye s>>
Repair the (K19) Ignition Coil Control No.1 circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 17
15.IGNITION COIL
Disconnect the Ignition Coil harness connector.
Remove the Fuel Pump Relay.
Using a 12-volt test light connected to 12-volts, probe the (K134) Coil
Control circuit.
Crank the engine for 5 seconds while observing the test light.
NOTE: The primary resistance of the 8.3L Ignition coil is 0.53 to
0.65 of an ohm at 77°F (25°C).
Does the test light brightly blink/flicker?
Ye s>>
Replace the Ignition Coil.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 16
16.COIL CONTROL CIRCUIT
Turn the ignition off.
Disconnect the PCM harness connector.
Check the (K134) Coil Control circuit for an open or short to ground.
Was a problem found with the Coil Control circuit?
Ye s>>
Repair the Coil Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 17