P034B
Crankshaft Position Sensor - Crankshaft Direction Incorrect
The crankshaft is rotating in the wrong direction relative to the expected reference — typically only seen on stop-start systems where the engine briefly counter-rotates after shutdown.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Stop-start residual reverse rotationCommon
Parts involved
- Crankshaft Position Sensor
P034B 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.