OBD-II Generic Error Code P0387: How to Fix It

Medium 1-2 hours Medium Severity Verified June 2026
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Error Code
P0387
Brand
OBD-II Generic
Product Type
automotive
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
1-2 hours
Error code P0387 indicates that the Engine Control Module (ECM) has detected a low voltage signal from the crankshaft position sensor B circuit. This sensor monitors crankshaft speed and position for engine timing and fuel injection. A low input can cause hard starting, stalling, or poor performance.
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Tools You'll Need

How to Fix Error Code P0387

  1. Check for Stored Codes and Freeze Frame Data

  2. Inspect Crankshaft Position Sensor Connector

    Ensure the ignition is off before disconnecting any sensor.

  3. Test Sensor Voltage Supply and Ground

    Be careful not to short pins while probing.

  4. Check Sensor Resistance

    Always consult your vehicle's service manual for exact values.

  5. Examine Wiring and Harness for Damage

  6. Replace Crankshaft Position Sensor (if needed)

    Torque the sensor bolt to manufacturer specification to avoid damage.

  7. Test Drive and Verify Repair

    If the code returns, further diagnosis of the ECM or crankshaft reluctor ring may be needed.

Parts You May Need

Crankshaft position sensor
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Electrical contact cleaner
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Crankshaft position sensor
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Electrical contact cleaner
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Crankshaft position sensor
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Electrical contact cleaner
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Crankshaft position sensor
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Electrical contact cleaner
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When to Call a Professional

If you are uncomfortable working with electrical systems or do not have the necessary tools, consult a professional mechanic. Also, if the problem persists after replacing the sensor, the ECM or reluctor ring may be faulty and requires advanced diagnostics.

Frequently Asked Questions

What does error code P0387 mean?
P0387 indicates the ECM has detected a low voltage signal from the crankshaft position sensor B circuit, which can affect engine timing and performance.
Can I drive with a P0387 code?
It is not recommended to drive with this code as the engine may stall or have reduced performance. It's best to diagnose and repair promptly.
How much does it cost to fix P0387?
The cost varies: replacing the crankshaft position sensor can be $80-$200 for parts and labor. DIY repair is cheaper if you have tools.
Where is the crankshaft position sensor located?
Typically near the crankshaft pulley, flywheel, or behind the harmonic balancer. Check your repair manual for exact location.
Can a bad crankshaft sensor cause no start?
Yes, if the sensor fails completely, the ECM may not receive crankshaft position data, preventing the engine from starting.

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