P0378
Fix within a few daysYour engine's computer is getting an intermittent or erratic signal from a timing reference sensor, specifically the 'B' high-resolution signal. This signal is critical for precise engine timing.
Code P0378 means your engine's timing reference signal is erratic. Common causes: Camshaft Position Sensor (60%), wiring issues (25%), Crankshaft Position Sensor (10%). Drivability: Limit driving, fix quickly. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0378?
Limit driving, fix within a few days
Essential trips under 10 miles, avoid highways and heavy acceleration. Be prepared for potential stalling.
Stop driving immediately if: Flashing CEL, engine stalls repeatedly, significant power loss, loud engine noises.
Symptoms of P0378
- 1Check Engine Light is on
- 2Engine cranks but won't start
- 3Engine stalls unexpectedly
- 4Rough idle or poor engine performance
- 5Reduced engine power or acceleration
- 6Engine misfires
Common Causes of P0378
Parts most likely causing this code, ranked by probability
A faulty camshaft position sensor sends incorrect or intermittent signals to the engine computer, disrupting timing calculations.
60% of P0378 cases are fixed by replacing this part
Damaged, corroded, or loose wiring and connectors prevent a clear signal from reaching the engine computer.
25% of P0378 cases are fixed by repairing wiring or connectors
An erratic crankshaft position sensor can also cause timing signal issues, as both sensors work together for engine timing.
10% of P0378 cases are fixed by replacing this part
A bent or damaged tooth on the camshaft or crankshaft reluctor wheel causes the sensor to read an inconsistent signal.
4% of P0378 cases are fixed by repairing or replacing the reluctor wheel
A rare but possible cause where the engine computer itself is unable to correctly process the timing signal.
1% of P0378 cases are fixed by replacing the ECM/PCM
Check These First (Before Buying Parts)
- Visually inspect the camshaft position sensor (CMP) and its electrical connector for any signs of damage, corrosion, or loose connections.
- Ensure the sensor is securely seated in its mounting location.
How to Diagnose P0378
- 1Visually inspect the camshaft position sensor (CMP) and its wiring harness for any obvious damage, fraying, or loose connections.
- 2Check for any Technical Service Bulletins (TSBs) related to P0378 for your specific vehicle make and model.
- 3Use a scan tool to monitor live data from the CMP and CKP sensors, looking for erratic readings or dropouts.
- 4Test the CMP sensor's resistance and voltage output according to your vehicle's service manual specifications.
- 5Inspect the reluctor wheel (tone ring) on the camshaft or crankshaft for damage or debris, if accessible.
- 6If all other components check out, consider testing the continuity of the wiring harness between the sensor and the ECM/PCM.
P0378 on Popular Vehicles
Toyota Camry
2007-2024Toyota Camry models can experience P0378 due to camshaft position sensor failure, often exacerbated by engine heat or age. Inspect the sensor and its connector carefully.
75% fixed by replacing CMP sensor or repairing wiring
Honda Accord
2003-2024Honda Accord vehicles are known to have issues with camshaft position sensors, which can trigger P0378. Check for oil leaks around the sensor, as oil can sometimes contaminate the electrical connection.
70% fixed by replacing CMP sensor or repairing wiring
Ford F-150
2004-2024Ford F-150 trucks, particularly those with VCT systems, can log P0378 from a faulty camshaft position sensor or issues with the wiring harness leading to it. Always check for proper sensor seating.
70% fixed by replacing CMP sensor or repairing wiring
Frequently Asked Questions
What does P0378 mean?
P0378 indicates that your engine's computer is receiving an intermittent or erratic signal from a critical timing reference sensor, specifically the 'B' high-resolution signal, which is essential for precise engine timing.
Can I drive with P0378?
Limit driving, fix within a few days. Driving with P0378 can lead to engine stalling, misfires, and potential damage to other engine components if the timing is severely off. Avoid long trips or high-speed driving.
Will P0378 clear itself?
No, P0378 will not clear itself. This code indicates a hard fault with a sensor or its circuit that requires diagnosis and repair. The Check Engine Light will remain on until the underlying issue is resolved.
How do I fix P0378 myself?
Start by visually inspecting the camshaft position sensor and its wiring for damage. If the wiring is good, replacing the camshaft position sensor is a common fix. You will need a scan tool to confirm the sensor's signal and clear the code.
How much does it cost to fix P0378?
DIY repair costs for P0378 are typically $50-$200 for a new camshaft position sensor. Professional shop repairs usually range from $150-$500, covering parts and labor for diagnosis and replacement.
P0378 keeps coming back - why?
P0378 keeps coming back because the initial repair did not address the root cause. This often happens if the wiring harness was overlooked, the reluctor wheel is damaged, or the wrong sensor was replaced. A thorough diagnosis is essential.
Will P0378 fail emissions/smog test?
Yes, P0378 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on, combined with a fault in a critical engine timing system, prevents the vehicle from passing inspection.
What's the difference between P0378 and P0340?
P0378 specifically indicates an intermittent or erratic high-resolution signal from a timing reference sensor (often a camshaft position sensor). P0340 is a more general code indicating a 'Camshaft Position Sensor Circuit Malfunction' which means the sensor circuit has a fault, but not necessarily an intermittent signal.
P0378 on Ford F-150
On Ford F-150s, P0378 often points to a failing camshaft position sensor or issues with its wiring, especially on engines with Variable Cam Timing (VCT). Always check for TSBs related to timing sensors for your specific engine.
Questions to Ask Your Mechanic
Did you check the live data from both the camshaft and crankshaft position sensors for erratic readings?
Good answer: Yes, I monitored both sensors and saw intermittent signal dropouts from the Bank 1 Camshaft Position Sensor, which points to the sensor itself or its wiring.
What did you find when you inspected the wiring harness and connector for the affected timing sensor?
Good answer: I found no visible damage or corrosion on the wiring or connector. I also performed a wiggle test to check for intermittent connections, and the signal remained stable during the test.
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 a scan tool for proper diagnosis and potentially a multimeter to test the sensor and wiring.
Cost of Waiting
Ignoring P0378 can lead to severe engine performance issues, including stalling and misfires. Continued driving with erratic timing signals can cause internal engine damage, such as bent valves or piston damage, turning a $100 sensor replacement into a multi-thousand dollar engine rebuild.
While You're In There...
Thoroughly inspect the wiring harness leading to the camshaft position sensor for any fraying, cuts, or signs of rodent damage, as this is a common cause of intermittent signals.
Tools You'll Need
- OBD-II scan tool
- Multimeter
- Basic hand tools (sockets, wrenches)
- Wiring diagram (vehicle-specific)
P0378 is a common sensor-related code. While it's important to address quickly, the repair is often straightforward, and your engine will run smoothly once fixed.
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Your Next Steps
Step 1: Visually inspect the camshaft position sensor and its wiring harness for any obvious damage or loose connections. Clean any visible corrosion.
Step 2: Use an OBD-II scan tool to monitor live data from the camshaft position sensor. Look for erratic readings or signal dropouts while the engine is running or cranking.
Step 3: If the sensor signal is erratic, test the sensor's resistance and voltage output with a multimeter. If the sensor tests bad or the wiring is damaged, replace the faulty component. Parts you'll likely need: new camshaft position sensor, or wiring repair kit.