P0387 — Crankshaft Position Sensor B Circuit Low Input
Drive with caution — fix soon.
What P0387 means
This code means the engine computer detected a low voltage signal from crankshaft position sensor B. It's typically caused by a shorted or grounded wire, a failing sensor, corroded connectors, or a poor ground. It's a common circuit fault and is usually fixed by repairing the wiring or replacing the sensor.
Common symptoms
- Check engine light is on
- Engine stalls or is hard to start
- Rough idle or misfires
- Hesitation or loss of power
- Intermittent no-start conditions
Common causes
- Shorted or grounded sensor signal wire
- Failing crankshaft position sensor B
- Corroded or damaged connector at the sensor
- Poor ground in the sensor circuit
- Wiring chafed against engine components
Typical repair cost
$150 – $500
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0387 code?
For short trips usually yes, but don't depend on it. The low signal can cause stalling or a no-start, so it's best to have it diagnosed and repaired before the sensor fails completely.
How much does it cost to fix a P0387 code?
Most repairs run $150 to $500. A wiring repair can be on the lower end, while replacing the sensor with labor lands toward the middle or higher of that range.
Is a P0387 code serious?
It's moderate. The engine may still run, but a low or dropping crankshaft signal can cause sudden stalling, so it's worth addressing without much delay.
Does P0387 mean the sensor itself is bad?
Not always. Low input often comes from a shorted wire, corroded connector, or bad ground rather than the sensor. A technician should check the wiring before condemning the sensor.