P0306

Diagnostic trouble code (DTC) information

Condition
The engine control module (ECM) checks engine combustion regarding misfire by registering speed deviations in flywheel rotation. If a certain number of misfires are detected for several cylinders during a certain number of crankshaft rotations, the misfires are considered emission-related or capable of damaging the catalytic converter and the diagnostic trouble code is generated.
The diagnostic trouble code can be diagnosed when the engine is running.
The trouble code indicates which cylinder is misfiring:
- ECM-P030100, cylinder 1 misfire.
- ECM-P030200, cylinder 2 misfire.
- ECM-P030300, cylinder 3 misfire.
- ECM-P030400, cylinder 4 misfire.
- ECM-P030500, cylinder 5 misfire.
- ECM-P030600, cylinder 6 misfire.

Substitute value
- Nothing.

Possible source
- Low fuel level.
- Repeated cold starts where the engine temperature does not reach proper operating temperature between starts.
- Damaged spark plug.
- Contaminated or wrong fuel.
- Wrong fuel grade (summer fuel in the winter, certain markets).
- Air leakage.
- Damaged VVT-unit.
- Clogged/leaking injector.
- Faulty fuel pressure.
- Uneven compression.

Fault symptom[s]
- Driving/Poor performance/lacks power/At take off
- Starting/Engine hard to start/cranks slowly/Unsure when/at all times
- Idling/Uneven idle
- Driving/Poor performance/lacks power
- Driving/Hesitates/surges/Unsure when/at all times
- Driving/Hesitates/surges/During acceleration
- Driving/Hesitates/surges/During deceleration
- Driving/Hesitates/surges/At steady speed
- Warning lights and chimes/Malfunction Indicator Light ("Check engine" light) indication/no indication
- Text window and warning symbol/Text message