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OBD Code P0387

Crankshaft Position Sensor B Circuit Low Input

CodeP0387
DescriptionCrankshaft Position Sensor B Circuit Low Input
Possible CausesShort to ground|Faulty sensor
SymptomsLoss of backup CKP signal
SystemIgnition

What Does P0387 Mean?

Crankshaft Position Sensor B Circuit Low Input. This diagnostic trouble code (DTC) is stored when the vehicle's onboard computer detects an issue with the ignition.

Code Breakdown

P = Powertrain code

0 = Generic (SAE standard)

How to Fix P0387

Follow these diagnostic steps to identify and resolve the issue. Always start with the simplest checks before moving to more involved repairs.

  1. Inspect the crankshaft position sensor connector for corrosion or damage.
  2. Check the sensor wiring for breaks, shorts, or chafing near the engine.
  3. Test the sensor resistance with a multimeter — compare to manufacturer spec.
  4. Inspect the sensor tone ring/reluctor on the crankshaft for damage.
  5. Check the air gap between the sensor and tone ring.
  6. Replace the crankshaft position sensor if faulty.
  7. Clear codes and verify the engine starts and runs smoothly.

Note: These are general diagnostic guidelines. Some vehicles may have model-specific procedures. Always consult your vehicle's service manual for exact specifications and torque values. If you are not comfortable performing these steps, visit a qualified mechanic.

Frequently Asked Questions

Is P0387 serious?

The severity depends on the underlying cause. Some triggers for P0387 are minor (like a loose gas cap), while others may indicate a more significant problem. We recommend having the code diagnosed with a proper scan tool to determine the exact cause before deciding on urgency.

Can I clear P0387 myself?

You can clear any OBD-II code with a code scanner or by disconnecting the battery for 15-30 minutes. However, clearing the code without fixing the underlying problem will cause it to return — usually within one or two drive cycles. If the code triggered the check engine light, the light will come back on. Fix the root cause first, then clear the code.

How much does it cost to fix P0387?

Repair costs vary widely depending on the root cause. Some fixes are free (like tightening a gas cap) while others can cost several hundred dollars (like replacing a catalytic converter or oxygen sensor). A proper diagnosis with a professional scan tool — not just reading the code — is the first step to getting an accurate repair estimate. Many auto parts stores offer free code reading, but a thorough diagnosis usually requires a mechanic.

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