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.
General code reference. Confirm the definition and diagnostic procedure for your vehicle's year, model and engine. A stored code alone does not identify a failed part.
Affected components
- Crankshaft position sensor
Possible causes to check
These are possible checks, not a ranked diagnosis. Follow the vehicle manufacturer's test procedure before replacing parts.
- Short to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
Related codes
Sources
Check each reference's vehicle and model-year scope. General background links do not establish which fault is most likely on your vehicle.
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.