Diagnostic trouble code P1377 is a manufacturer-specific powertrain fault code. Because it is manufacturer-specific, its exact definition depends entirely on the vehicle make, model, and application.
Exact vehicle application must be verified before diagnosis. The code identifies a detected condition in a specific subsystem, but further testing is required to identify the root cause.
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Key Takeaways
- P1377 is a manufacturer-specific code, meaning its definition varies between automakers like General Motors, Volkswagen, and BMW.
- On GM applications, it indicates an ignition control module cam pulse to 4X reference pulse comparison fault.
- On VW and Audi applications, it points to a cylinder 8 ignition coil short to positive.
- On BMW applications, it may indicate a camshaft position sensor master camshaft not defined fault.
- Diagnosis requires verifying the exact factory definition and testing the relevant ignition or sensor circuits.
P1377 Code Description and Implications
Because P1377 is manufacturer-specific, there is no single universal definition. This fault code identifies a detected condition, but the exact monitored system depends on the vehicle make and model.
Some General Motors applications: P1377 indicates an “Ignition Control (IC) Module Cam Pulse to 4X Reference Pulse Comparison” fault. The module detects a mismatch between the camshaft reference pulse and the 4X crankshaft reference pulse.
Some Volkswagen and Audi applications: P1377 indicates an “Ignition Coil/Amplifier Cylinder 8 Short to Positive” fault, pointing to an electrical short to voltage in the ignition control circuit for cylinder 8.
Some BMW applications: P1377 may indicate a “Camshaft Position Sensor Master Camshaft Not Defined” fault, relating to an issue with the camshaft position sensor signal synchronization.
Common Causes of the P1377 Code
The underlying cause depends entirely on the verified factory definition for the specific vehicle application.
For GM applications, possible causes include a failing camshaft position sensor, a faulty crankshaft position sensor, damaged wiring in the reference circuits, or a failing ignition control module.
For VW and Audi applications, causes may involve a failing ignition coil on cylinder 8, damaged ignition coil wiring, or poor electrical connections at the coil harness causing a short to positive.
For BMW applications, causes can include a failing camshaft position sensor, damaged sensor wiring, or poor electrical connections at the sensor harness.
Symptoms Associated With P1377
Symptoms vary widely depending on the underlying system fault and the vehicle manufacturer.
On GM applications with a reference pulse comparison fault, symptoms can include engine stalling, rough idling, reduced power, and an illuminated Check Engine Light.
On VW and Audi applications with a cylinder 8 ignition short, symptoms may include a severe misfire on cylinder 8, hesitation during acceleration, and limp mode activation.
On BMW applications, symptoms can include rough idling, hesitation during acceleration, and a no-start condition if the camshaft position signal is lost.
Diagnosing the P1377 Trouble Code
Diagnosis must begin by confirming the exact factory definition for the specific make, model, and year.
For GM applications, technicians inspect the camshaft and crankshaft position sensor wiring for opens or shorts, test the sensor signals using an oscilloscope, and verify the ignition control module operation.
For VW and Audi applications, technicians test the ignition coil primary circuit for cylinder 8 for shorts to voltage, inspect the wiring harness, and verify the engine control module output.
For BMW applications, technicians test the camshaft position sensor circuits, inspect the wiring harness, and verify the sensor signal synchronization.
Repairing the P1377 Issue
Repairs must follow confirmed diagnosis based on the specific vehicle application.
If a reference pulse fault is confirmed on a GM application, the damaged wiring must be repaired, or the camshaft/crankshaft position sensor or ignition control module replaced.
If an ignition coil short is confirmed on a VW or Audi, the damaged wiring must be repaired or the cylinder 8 ignition coil replaced.
If a camshaft position sensor fault is confirmed on a BMW, the sensor or damaged wiring must be replaced or repaired.
Cost Considerations for P1377 Repairs
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Replacing a camshaft position sensor or ignition coil may require minimal labor depending on accessibility.
Conversely, diagnosing intermittent wiring faults or replacing sensors buried behind engine components requires significant labor.
Prevention Strategies for Future Occurrences
Some electrical and mechanical failures cannot be reliably prevented.
Inspecting exposed wiring harnesses for chafing or heat damage can help prevent intermittent circuit faults in the camshaft sensor or ignition control systems.
Keeping connector seals intact may reduce moisture intrusion that leads to corrosion and signal loss.
Troubleshooting Tips and Best Practices
Never assume P1377 is a universal camshaft sensor code. Always verify the exact definition for the specific vehicle before purchasing parts.
Do not ignore related codes. A reference pulse fault may appear alongside crankshaft position sensor codes or specific cylinder misfire codes.
Check for technical service bulletins applicable to your exact vehicle application, as manufacturers frequently release updated sensors or revised wiring harnesses for recurring faults.
More OBD-II Codes
| P1376 | P1378 | P0335 | P0171 |
| P1375 | P1380 | P0340 | P0174 |
| P1374 | P1381 | P0300 | P1108 |
| P1373 | P1382 | P1345 | P1109 |
| P1372 | P1386 | P1344 | P1346 |
| P1371 | P1387 | P1347 | P1348 |
Frequently Asked Questions
Is P1377 a generic or manufacturer-specific code?
No. P1377 is a manufacturer-specific code. Its exact definition varies significantly between automakers, so the factory service information for the specific vehicle must be consulted.
Can I drive my car with a P1377 code?
It depends on the application. If P1377 indicates a reference pulse comparison fault, the engine may stall. If it is an ignition coil short, performance may be reduced.
Will disconnecting the battery clear the P1377 code?
Disconnecting the battery may temporarily clear the code, but it does not repair the underlying electrical or mechanical fault. The code will return once the monitor runs again.
Can a bad camshaft position sensor cause a P1377 code?
On GM applications monitoring the reference pulses, a failing camshaft position sensor can prevent the correct pulse correlation, triggering the fault code.
Does P1377 always mean the ignition control module is bad?
No. While a failing module is a cause on specific GM applications, the code can also indicate damaged wiring, a failing camshaft position sensor, or an ignition coil short.
What Should You Do About the P1377 Code?
Confirm the exact factory definition and diagnostic procedure for your specific vehicle application. Because P1377 is manufacturer-specific, identifying whether it relates to a reference pulse comparison fault or an ignition coil short is mandatory.
Follow the applicable manufacturer diagnostic steps to test the relevant system and components. Once the root cause is confirmed, complete the necessary repairs and verify that the system operates correctly and the code does not return.
