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For 1990-2009 cars only

System Description

The powertrain control module (PCM) uses information from the crankshaft position (CKP) sensors and from the camshaft position (CMP) sensor in order to determine if engine misfire is occurring. By monitoring the variations in the crankshaft rotational speed for each cylinder, the PCM is able to detect individual cylinder misfire events. A misfire rate that is high enough can cause damage to the 3-way catalytic converter. The malfunction indicator lamp (MIL) will flash if converter-damaging conditions are present.

Conditions for Running the DTC

    • DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0335, P0336, P0341, P0342, P0343, P0500, P0502, P0503, and P1258 are not set.
    • The engine speed is between 450-3,001 RPM.
    • The ignition voltage is between 10-18 volts.
    • The engine coolant temperature is between -7°C (19°F)-130°C (266°F).
    • The fuel level is more than 10 percent.
    • The throttle position (TP) sensor angle is steady within 1 percent.
    • The anti-lock brake system (ABS) system and the traction control system are not active.
    • The transmission is not changing gears.
    • The secondary air injection (AIR) diagnostic test is not in progress.
    • The A/C clutch is not changing states.
    • The PCM is not in fuel shut-off mode or decel fuel cut-off mode.
    • The ABS signals not exceeding the rough road thresholds.

Conditions for Setting the DTC

    • The PCM determines that an emissions-type misfire is present.
    • The PCM determines that a catalyst-damaging misfire is present.

Action Taken When the DTC Sets

    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Important: 

   • Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when you diagnose or replace the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
   • For any test that requires probing the PCM or component harness connectors, use the J 35616 connector test adapter kit . Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems.

The following conditions may cause a misfire:

    • Running the vehicle out of fuel causes sufficient misfire to set DTC P0300. A vehicle that is out of fuel may have DTC P0461 also set.
    • A restricted fuel filter can cause sufficient misfire to set DTC P0300. Refer to Fuel System Diagnosis .
    • A misfire may not be apparent at idle. The misfire may only occur above idle under a load. Road-test the vehicle, and monitor the misfire current counters.
    • If more than one cylinder is mis-firing, the scan tool may only display one cylinder mis-firing. This condition will not be apparent until you complete the repair. Also, if an ignition coil or module ground circuit is open for one side of the engine, the scan tool may only display 2 or 3 cylinders mis-firing. Inspect the ground circuit for the ignition coil or modules on the cylinder bank of the engine that has more than one cylinder mis-firing.
    • Excessive vibration from sources other than the engine could cause a misfire DTC. The following conditions are possible sources of vibration:
       - A variable thickness brake rotor
       - A drive shaft that is not balanced
       - Certain rough road conditions

For an intermittent condition, refer to Intermittent Conditions .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. A misfire may not be apparent at idle. The misfire may only occur above idle or under a load. Road-test the vehicle, and monitor the Misfire Current Counters.

    If certain DTCs set at the same time or after DTC P0300 sets, the Misfire Current Counters will not increment . Refer to conditions for running DTC P0300 for the applicable DTC list.

    If more than one cylinder is misfiring, the Misfire Current Counters may increment for only one cylinder. For example, cylinder 1 and cylinder 8 are both misfiring, but only Cylinder 8 increments on the Misfire Current Counter.

    If one injector fuse is open, only 2 or 3 Misfire Current Counters may increment for the corresponding side of the engine.

    Wetting the secondary ignition system with water from a spray bottle may help to locate the damaged or deteriorated components. When you apply the water, look and listen for arcing or misfiring.

    If the Misfire Current Counters are incrementing and there is no apparent misfire, an erratic CKP sensor signal could be the cause. If you suspect that this condition exists, perform the diagnostic test for DTC P0335 first.

    If a misfire is present and you suspect a fuel control condition, force the fuel system into Open Loop using the scan tool, and allow the engine to run for a few minutes. If this procedure eliminates the misfire, refer to any fuel control related DTCs which are set. If no other DTCs are set, refer to the Engine Scan Tool Data List.

  2. The cylinder with the more significant misfire may cause another cylinder's counter to increment by only a small amount.

  3. If the engine misfire moves with the spark plug, this is good indication that you should replace the spark plug.

  4. If you cannot locate a fuel system condition, refer to Engine Mechanical - 5.7L. An engine mechanical condition can cause a spark plug to gas foul. Inspect for loose rockers, and inspect for collapsed lifters or for worn camshaft lobes.

  5. If the customer's concern is that the MIL is flashing, this indicates that a Catalyst Misfire has occurred. Drive the vehicle in the conditions to run the catalyst diagnostic.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: 

   • You must perform the CKP System Variation Learn Procedure before proceeding with this diagnostic table. Refer to Crankshaft Position System Variation Learn .
   • Before you proceed with this diagnostic, ensure that the ABS system and the Traction Control system are functioning properly.
   • If any DTCs, other than P0135 and P0155 are set, refer to those DTCs before proceeding with this diagnostic.

Use the scan tool in order to monitor all the Misfire Current Counters on the misfire data list. There are 8 counters, with one counter per cylinder.

Are any of the Misfire Current Counters incrementing?

--

Go to Step 4

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. Review the Freeze Frame/Failure Records data for this DTC, and observe the parameters.
  3. Turn OFF the ignition for 15 seconds.
  4. Start the engine.
  5. Operate the vehicle within the conditions required for this diagnostic to run. Attempt to duplicate the conditions recorded in the Freeze Frame/Failure Records. Special operating conditions that you must meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
  6. Select the Diagnostic Trouble Code (DTC) option.

Does the scan tool indicate that this diagnostic failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

Is only one Misfire Counter incrementing?

--

Go to Step 6

Go to Step 5

5

Inspect the following items:

    • Observe the HO2S readings on the scan tool.
        If the signal is fixed below 200 mV refer to DTC P0131 or P0151 .
        If the signal is fixed above 900 mV refer to DTC P0132 or P0152 .
    • Inspect the accessory drive belt and the pulleys for damage or misalignment. Refer to Drive Belt Excessive Wear Diagnosis in Engine Mechanical-5.7L.
    • Inspect the vacuum hoses for splits, for kinks, and for correct connections. Refer to Emission Hose Routing Diagram .
    • Inspect the throttle body and the intake manifold for vacuum leaks.
    • Inspect the crankcase ventilation valve and/or system for vacuum leaks. Refer to Crankcase Ventilation System Inspection/Description in Engine Mechanical-5.7L .
    • Inspect the PCM grounds for being clean and secure. Refer to Ground Distribution Schematics in Wiring Systems.
    • Verify that all injector harness connectors are connected to the proper injector and/or cylinder.
    • Inspect the injector and the Ignition Control fuses for being open. If you find an open fuse, locate and repair the shorted circuit. Refer to Wiring Repairs in Wiring Systems.
    • Test for low fuel pressure or for restricted fuel flow. Refer to Fuel System Diagnosis .
    • Inspect for a restricted exhaust. Refer to Restricted Exhaust in Engine Exhaust.
    • Inspect for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Did any of the above tests isolate a condition requiring a repair?

--

Go to Step 17

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Disconnect the injector that corresponds to any Misfire Current Counter that was incrementing.
  3. Connect the J 34730-2C injector test lamp to the injector electrical connector.
  4. Idle the engine.

Is the injector test lamp flashing?

--

Go to Step 7

Go to DTC P0200

7

  1. Turn OFF the ignition.
  2. Reconnect the injector harness electrical connector.
  3. Disconnect the ignition wires from any spark plug that corresponds to any Misfire Current Counter that is incrementing.
  4. Install J 26792 spark tester to ground.
  5. Start the engine.

Does the spark jump the tester gap, and is the spark consistent?

--

Go to Step 9

Go to Step 8

8

  1. Remove the ignition wire for the cylinder that is misfiring.
  2. Use the DMM in order to measure the resistance of the ignition wire.

Is the ignition wire resistance less than the specified resistance?

700 ohms

Go to Electronic Ignition (EI) System Diagnosis

Go to Step 16

9

  1. Remove the spark plugs from the cylinder that indicated a misfire. Refer to Ignition Coil Replacement .
  2. Inspect the spark plugs. Refer to Spark Plug Inspection .

Does the spark plug appear to be OK?

--

Go to Step 10

Go to Step 11

10

Important:  If the Injector Coil Test Procedure does not isolate the condition, refer to Base Engine Misfire without Internal Engine Noises in Engine Mechanical-5.7L.

  1. Swap the suspected spark plug with another cylinder that is operating properly.
  2. Operate the vehicle under the same conditions that the misfire occurred.

Did the misfire move with the spark plug?

--

Go to Step 15

Go to Fuel Injector Solenoid Coil Test

11

Are the spark plugs oil or coolant fouled?

--

Go to Base Engine Misfire with Coolant Consumption or Base Engine Misfire with Excessive Oil Consumption in Engine Mechanical-5.7L

Go to Step 12

12

Important:  If the Fuel System is OK, refer to Base Engine Misfire without Internal Engine Noises in Engine Mechanical-5.7L.

Are the spark plugs gas-fouled?

--

Go to Fuel System Diagnosis

Go to Step 13

13

Important:  If the Injector Coil Test Procedure does not isolate the condition, refer to Base Engine Misfire without Internal Engine Noises in Engine Mechanical-5.7L.

Do the spark plugs show any signs of being cracked, worn, or improperly gapped?

--

Go to Step 14

Go to Fuel Injector Solenoid Coil Test

14

  1. Replace or re-gap spark plugs.
  2. If improper gap is found, be sure to re-gap spark plugs using a wire type gauge.

Is the action complete?

--

Go to Step 17

--

15

Replace the faulty spark plugs. Refer to Spark Plug Replacement .

Did you complete the replacement?

--

Go to Step 17

--

16

Replace the faulty ignition wires. Refer to Spark Plug Wire Replacement .

Did you complete the replacement?

--

Go to Step 17

--

17

Was the customer's concern that the MIL was flashing?

--

Go to DTC P0420 or P0430

Go to Step 18

18

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 19

Go to Step 2

19

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK