Circuit/System Verification
Before starting the engine, review the freeze frame failure records data to determine if the misfire sets during a cold start or at operating temperature. If there is a cold start condition and the engine is started, the engine will need to be cooled down before the next attempt to start the engine within the fail conditions.
If this a hybrid application and the hybrid battery is fully charged, the engine runs at a very low load since the hybrid battery cannot accept any additional charge. At this very low engine load, engine misfire may not be detected. It may be necessary to drive the vehicle in battery only propulsion mode in order to discharge the hybrid battery before diagnosis can be performed.
- If this is a hybrid application, skip to step 4.
- Engine Running at normal operating temperature.
- Verify there is no abnormal engine noise.
- If abnormal engine noise is present
Refer to Symptoms - Engine Mechanical .
- Go to next step: If abnormal engine noise is not present
- If abnormal engine noise is present
- Perform the scan tool Crankshaft Position Variation Learn procedure.
- Verify no DTCs are set.
- If any DTCs other than P0300 - P0304 are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- If DTC P0300 - P0304 is set
Refer to Circuit/System Testing below.
- Go to next step: If no DTCs are set
- If any DTCs other than P0300 - P0304 are set
- Verify the scan tool Cylinder 1 - 4 Current Misfire Counter parameters do not increment.
- If increments
Refer to Circuit/System Testing below.
- Go to next step: If does not increment
- If increments
- Engine Running, perform the Cylinder Power Balance Test with a scan tool.
- Verify the engine speed changes when each injector is disabled and then enabled.
- If engine speed does not change
Refer to Circuit/System Testing below.
- Go to next step: If engine speed does change
- If engine speed does not change
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
- Verify the DTC does not set.
- If the DTC sets
Refer to Circuit/System Testing below.
- Go to next step: If the DTC does not set
- If the DTC sets
- All OK.