P0377
Fix within a few daysTiming Reference High Resolution Signal B Too Low/Too Few Pulses
Code P0377 means your engine's high-resolution timing signal B is too low. Common causes: Camshaft Position Sensor B (70%), wiring issues (20%). Drivability: No, stop driving. Repair cost: $70-$250 DIY, $150-$600 professional.
Can I Drive With P0377?
No, stop driving
Immediate repair needed
Stop driving immediately if: Flashing CEL, engine stalls, engine won't start, significant power loss, loud engine noises.
Symptoms of P0377
- 1Engine cranks but won't start
- 2Engine stalls unexpectedly while driving
- 3Rough idle or poor engine performance
- 4Reduced engine power
- 5Engine misfires
- 6Check Engine Light is on
Common Causes of P0377
Parts most likely causing this code, ranked by probability
The sensor itself is faulty, sending a weak or intermittent signal to the engine computer.
70% of P0377 cases are fixed by replacing this part
Damaged, corroded, or loose wiring/connector prevents the sensor signal from reaching the engine computer correctly.
20% of P0377 cases are fixed by repairing this wiring
A damaged or misaligned reluctor wheel on the camshaft prevents the sensor from accurately reading engine position.
8% of P0377 cases are fixed by addressing the reluctor wheel
The engine computer itself is faulty and cannot correctly interpret the camshaft position sensor signal.
2% of P0377 cases are fixed by replacing the ECM/PCM
Check These First (Before Buying Parts)
- Visually inspect the Camshaft Position Sensor B and its electrical connector for any signs of damage, corrosion, or loose connections.
- Ensure the engine oil level is correct, as low oil can sometimes affect VVT systems that rely on oil pressure.
How to Diagnose P0377
- 1Visually inspect the Camshaft Position Sensor B and its wiring for any obvious damage, fraying, or corrosion.
- 2Check the electrical connector at the sensor for a tight fit and clean pins.
- 3Use a multimeter to check for proper voltage supply to the sensor and signal return to the ECM.
- 4If possible, use an oscilloscope to check the actual waveform signal from the sensor for proper pulse generation.
- 5If wiring and power supply are good, replace the Camshaft Position Sensor B.
P0377 on Popular Vehicles
Ford F-150
2004-2024P0377 on Ford F-150 trucks often points to a failing Camshaft Position Sensor on Bank 1, exhaust side (if applicable). Wiring harness damage from rodents is also a common culprit.
75% fixed by replacing CMP B or repairing wiring
Chevrolet Silverado
2007-2024For Chevrolet Silverado, P0377 typically indicates an issue with the Camshaft Position Sensor B. These sensors are critical for the Variable Valve Timing (VVT) system. Always check the sensor's electrical connector for corrosion.
70% fixed by replacing CMP B
Honda Accord
2003-2024On Honda Accord models, P0377 is less common but when it appears, it's almost always a faulty Camshaft Position Sensor B or a wiring issue leading to it. Ensure the sensor is a quality OEM or equivalent replacement.
80% fixed by replacing CMP B
Frequently Asked Questions
What does P0377 mean?
P0377 indicates that the engine computer is receiving a signal from the 'B' timing reference sensor (usually a camshaft position sensor) that is too low or has too few pulses. This signal is critical for precise engine timing and fuel delivery.
Can I drive with P0377?
No, stop driving. A P0377 code means your engine's timing reference is compromised. This can lead to sudden stalling, no-start conditions, or severe engine damage if the timing is incorrect. Get it fixed immediately.
Will P0377 clear itself?
No, P0377 will not clear itself. This code points to a hard fault with a critical sensor or its circuit. The underlying issue must be diagnosed and repaired for the code to clear, either automatically after several drive cycles or by using a scan tool.
How do I fix P0377 myself?
Start by visually inspecting the Camshaft Position Sensor B and its wiring for damage. Check the connector for corrosion. If everything looks good, the most common fix is replacing the Camshaft Position Sensor B. This often involves removing a bolt and unplugging a connector.
How much does it cost to fix P0377?
A DIY fix for P0377, primarily replacing the Camshaft Position Sensor B, costs $70-$250 for the part. If you take it to a shop, expect to pay $150-$600, which includes parts and labor.
P0377 keeps coming back - why?
If P0377 keeps returning, the initial repair did not address the root cause. This often means the issue is not the sensor itself but rather damaged wiring, a corroded connector, a faulty reluctor wheel, or, in rare cases, a problem with the engine computer.
Will P0377 fail emissions/smog test?
Yes, P0377 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 fault with a critical engine sensor like this directly impacts engine efficiency and emissions.
What's the difference between P0377 and P0376?
P0377 indicates that the 'B' timing reference signal has too few pulses or is too low, suggesting a weak or missing signal. P0376 indicates the 'B' timing reference signal has too many pulses or is too high, suggesting an electrical short or interference.
P0377 on Ford F-150?
On a Ford F-150, P0377 most commonly points to a failing Camshaft Position Sensor B. These sensors can degrade over time, especially with high mileage. Always check the wiring for rodent damage, which is common in trucks.
Questions to Ask Your Mechanic
Did you check the signal waveform from the Camshaft Position Sensor B with an oscilloscope?
Good answer: Yes, the waveform showed intermittent drops/low voltage, confirming the sensor or its circuit is faulty.
What did you find when inspecting the wiring harness to the Camshaft Position Sensor B?
Good answer: We found no visible damage or corrosion, and continuity checks confirmed the wiring is good from the sensor to the ECM.
Repair Cost Estimate
DIY Repair
Parts only
$70-$250
Shop Repair
Parts + labor
$150-$600
Save $80-$350 by doing it yourself
Difficulty
intermediate
Time
0.5-2 hours
Intermediate - requires basic electrical diagnostic skills and the ability to locate and replace the sensor, which can be in a tight spot.
Cost of Waiting
Ignoring P0377 can lead to your engine stalling unexpectedly, leaving you stranded. Continued driving with incorrect timing can cause severe internal engine damage, such as bent valves or piston damage, turning a $100 sensor replacement into a $3,000+ engine rebuild.
While You're In There...
If the sensor is related to VVT, clean oil is crucial for proper operation, and it's a good maintenance item.
If the sensor requires removing the valve cover, replacing the gasket prevents future oil leaks and saves labor.
Tools You'll Need
- OBD-II scan tool
- Basic socket set
- Screwdriver set
- Multimeter (for electrical checks)
- Wire strippers/crimpers (if wiring repair is needed)
P0377 is a serious code because it affects engine timing, but the fix is often a straightforward sensor replacement. Once repaired, your engine will run smoothly and reliably again.
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Your Next Steps
Step 1: Visually inspect the Camshaft Position Sensor B and its wiring. Look for frayed wires, melted insulation, or a loose/corroded connector.
Step 2: If the visual inspection doesn't reveal an obvious issue, use a multimeter to check for proper voltage supply to the sensor and signal continuity back to the ECM. If the wiring is good, proceed to sensor replacement.
Step 3: Parts you'll likely need: A new Camshaft Position Sensor B.