P0387
Crankshaft Position Sensor B Circuit Low
Crank sensor B below lower plausibility — short to ground. The crankshaft position sensor provides RPM and crank angle — without a valid signal, no ignition and no injection. Engine will not start or stalls instantly.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Short to groundCommon
- Connector pins corroded - high contact resistanceLess likely
- Harness chafing through insulationLess likely
Parts involved
- Crankshaft Position Sensor
P0387 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.