P050B
Cold Start Ignition Timing Performance
During cold-start the ECU retards ignition timing to raise exhaust temperature for catalyst light-off. The strategy does not deliver the expected timing - feedback from knock sensor or combustion model shows ignition too far advanced or retarded for the demanded calibration.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Knock sensor drift causes wrong feedbackCommon
- Cam phaser offset against crankPossible
Parts involved
- Ignition Timing Strategy
- Knock Sensor
- Cam Position Sensor
P050B is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.