P0387
Crankshaft Position Sensor B Circuit Low
Crank/cam position
Generic OBD-II
High
What it means
P0387 means the "B" crankshaft position sensor circuit is reading abnormally low voltage. This sensor helps the computer track engine speed and crank position for spark and fuel timing, so a fault can cause hard starting, stalling, or a no-start — most often from wiring, the connector, or the sensor itself.
High
Can I keep driving? Risky — a crank sensor circuit fault can cause hard starting, stalling, or a no-start; repair it promptly.
Common symptoms
What you'll notice
- Check-engine light on
- Hard starting, no-start, or intermittent stalling
- Rough idle or hesitation
- Occasional cutting out while driving
Common causes
Most likely first
- Corroded, loose, or damaged connector at the 'B' crankshaft position sensorLikely
- Open or shorted (low) wiring in the sensor circuitCommon
- Faulty crankshaft position sensor BCommon
- Damaged reluctor/tone ring or debris on the sensor tipLess often
- ECM fault (rare)Less often
How to diagnose & fix
Work through it in order
- Inspect the crank sensor B connector and harness for corrosion, chafing, or a short to ground.
- Check the sensor tip and reluctor ring for damage or metal debris.
- Back-probe the circuit and compare the signal/voltage to spec while cranking.
- Replace the crankshaft position sensor if faulty, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0387?+
Not reliably — the crank signal is essential for spark and fuel timing, so the engine can stall or fail to start unexpectedly.
Can I just clear P0387?+
It returns when the fault reappears and won't stop a stall. Repair the wiring or sensor first.
Related codes
Often seen with P0387
Read & clear P0387 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX