P0387
Stop drivingThe engine's computer detects a low voltage or erratic signal from the 'B' crankshaft position sensor circuit. This sensor is critical for engine timing and fuel injection.
Code P0387 means your engine's crankshaft position sensor 'B' circuit has a low or erratic signal. Common causes: Faulty sensor (60%), wiring issues (30%). Drivability: No, stop driving immediately. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0387?
No, stop driving
Immediate repair needed
Stop driving immediately if: Engine stalls, won't start, or the Check Engine Light is flashing.
Symptoms of P0387
- 1Engine cranks but won't start
- 2Engine stalls unexpectedly while driving
- 3Rough idle or misfires
- 4Reduced engine power
- 5Check Engine Light is on, possibly flashing
Common Causes of P0387
Parts most likely causing this code, ranked by probability
The sensor itself is faulty, sending a weak, intermittent, or incorrect signal to the engine computer.
60% of P0387 cases are fixed by replacing this part
Damaged, corroded, or loose wiring and connectors in the crankshaft position sensor circuit can cause a low or erratic signal.
30% of P0387 cases are fixed by repairing wiring or connectors
Physical damage, debris, or misalignment of the tone ring (the notched wheel the sensor reads) can cause an incorrect signal.
8% of P0387 cases are fixed by addressing tone ring issues
A rare internal fault within the engine's computer can incorrectly interpret or process the sensor's signal.
2% of P0387 cases are fixed by replacing the ECM/PCM
Check These First (Before Buying Parts)
- Visually inspect the crankshaft position sensor's wiring and connector for any signs of damage, corrosion, or looseness.
- Ensure the battery is fully charged and the terminals are clean and tight, as low voltage can sometimes mimic sensor issues.
How to Diagnose P0387
- 1Visually inspect the crankshaft position sensor and its wiring harness for any obvious damage, fraying, or loose connections.
- 2Check the sensor's electrical connector for corrosion, bent pins, or proper seating.
- 3Using a multimeter, test the sensor's resistance and voltage output according to your vehicle's service manual specifications.
- 4If accessible, inspect the crankshaft tone ring (reluctor wheel) for any physical damage, missing teeth, or debris.
- 5If all other components check out, consider professional diagnosis of the Engine Control Module (ECM/PCM).
P0387 on Popular Vehicles
Toyota Camry
2007-2024Crankshaft position sensor failures are not extremely common but can occur. Access is generally straightforward on 4-cylinder engines, often located near the oil filter or front of the engine. Wiring integrity is key.
75% fixed by replacing the sensor or repairing wiring
Honda Accord
2003-2024Honda engines are sensitive to proper sensor signals. The CPS is typically located on the lower front of the engine block. Pay close attention to the harness where it might rub against other components, causing wiring damage.
70% fixed by replacing the sensor or repairing wiring
Ford F-150
2004-2024On F-150s, the crankshaft position sensor can be in varying locations depending on the engine (V6 or V8). Wiring can be exposed to road debris or heat, leading to intermittent connection issues. Always check the tone ring for damage during diagnosis.
65% fixed by replacing the sensor or repairing wiring
Frequently Asked Questions
What does P0387 mean?
P0387 indicates that your vehicle's engine computer has detected a low voltage or an inconsistent signal from the 'B' circuit of the crankshaft position sensor. This sensor is vital for the engine to know the exact position and speed of the crankshaft, which it uses for precise fuel injection and ignition timing.
Can I drive with P0387?
No, stop driving. A P0387 code means the engine's computer is not getting a reliable signal from a critical sensor. This can lead to sudden engine stalling, misfires, or a no-start condition, which is dangerous and can cause further engine damage.
Will P0387 clear itself?
No, P0387 will not clear itself. This code indicates a hard fault with a critical sensor or its circuit. The underlying issue must be diagnosed and repaired before the code will clear, either automatically after several drive cycles or by using an OBD-II scan tool.
How do I fix P0387 myself?
Start by visually inspecting the crankshaft position sensor and its wiring for damage. If the wiring looks good, you'll likely need to replace the crankshaft position sensor itself. Access to the sensor can vary greatly by vehicle, sometimes requiring removal of other components.
How much does it cost to fix P0387?
The cost to fix P0387 ranges from $50-$200 for DIY, primarily for the part. Professional repair costs typically range from $150-$500, including parts and labor, depending on the vehicle and sensor location.
P0387 keeps coming back - why?
If P0387 keeps returning, it means the root cause wasn't fully addressed. Common reasons include a faulty replacement sensor, overlooked wiring damage further up the harness, a damaged tone ring, or, in rare cases, an issue with the engine's computer (ECM/PCM).
Will P0387 fail emissions/smog test?
Yes, P0387 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on is an automatic failure in most jurisdictions, and a faulty crankshaft position sensor directly impacts engine performance and emissions.
What's the difference between P0387 and P0335?
P0335 is a general code indicating a malfunction in the crankshaft position sensor circuit. P0387 is more specific, pointing to a 'low' signal condition or an issue with the 'B' circuit of the crankshaft position sensor. While both relate to the CPS, P0387 narrows down the type of signal problem.
P0387 on Ford F-150?
On many Ford F-150 models, the crankshaft position sensor is located near the front or side of the engine block, often requiring some disassembly for access. Wiring issues due to heat or vibration are common, so thoroughly inspect the harness and connector before replacing the sensor.
Questions to Ask Your Mechanic
Did you check the crankshaft position sensor's signal with an oscilloscope to confirm the low voltage condition?
Good answer: Yes, we hooked up the scope and saw the signal drop out or stay below the expected voltage range, confirming the sensor or its circuit is faulty.
What did you find when inspecting the wiring harness and connector for the crankshaft position sensor?
Good answer: We found some corrosion in the connector pins, or a section of the wire insulation was chafed, causing an intermittent short.
Repair Cost Estimate
DIY Repair
Parts only
$50-$200
Shop Repair
Parts + labor
$150-$500
Save $100-$300 by doing it yourself
Difficulty
intermediate
Time
1-3 hours
Intermediate - requires basic diagnostic tools like a multimeter and potentially some disassembly to access the sensor, which can be challenging depending on the vehicle.
Cost of Waiting
Ignoring P0387 means your engine can stall unexpectedly at any time, creating a dangerous driving situation. Continued operation with an erratic signal can also lead to incorrect ignition timing, potentially causing engine damage over time.
While You're In There...
If the sensor is located in an area prone to oil leaks or requires draining oil for access, it's a good time for an oil change.
If the repair requires removing accessories or covers that block access to the serpentine belt, inspect its condition and consider replacement if it's worn.
Tools You'll Need
- OBD-II Scan Tool
- Basic Hand Tools (sockets, wrenches)
- Multimeter
- Jack and Jack Stands (for access)
- Safety Glasses
- Wire Brush (for cleaning connectors)
P0387 points to a specific sensor issue that is critical but often straightforward to diagnose and fix. Once repaired, your engine's timing will be restored, and it will run reliably again.
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Your Next Steps
Step 1: Perform a thorough visual inspection of the crankshaft position sensor, its wiring harness, and the electrical connector. Look for any cuts, fraying, corrosion, or loose connections.
Step 2: If the visual inspection doesn't reveal an obvious issue, use a multimeter to test the sensor's resistance and voltage output. Compare readings to your vehicle's service manual specifications.
Step 3: If the sensor tests faulty or the wiring is damaged, you'll likely need to replace the crankshaft position sensor or repair the wiring. Parts you'll likely need: 1 Crankshaft Position Sensor.