Diagnostic trouble code P1387 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
- P1387 is a manufacturer-specific code, meaning its definition varies between automakers like Volkswagen, Ford, and Honda.
- On VW and Audi applications, it indicates an internal malfunction of the control unit altitude sensor.
- On Ford and Mazda applications, it points to a Variable Cam Timing (VCT) solenoid #2 circuit malfunction.
- On Honda and Acura applications, it indicates a Cylinder Position (CYP) Sensor B no signal fault.
- Diagnosis requires verifying the exact factory definition and testing the relevant sensor or solenoid circuits.
P1387 Code Description and Implications
Because P1387 is manufacturer-specific, there is no single universal definition. This error code identifies a detected condition, but the exact monitored system depends on the vehicle make and model.
Some Volkswagen and Audi applications: P1387 indicates an “ECM Altitude Sensor Internal Malfunction,” meaning the engine control module detects an internal fault with the barometric pressure sensor integrated into the module.
Certain Ford and Mazda applications: P1387 indicates a “Variable Cam Timing Solenoid #2 Circuit Malfunction,” pointing to an electrical issue in the VCT solenoid control circuit for bank 2 or the second solenoid.
Some Honda and Acura applications: P1387 indicates a “CYP Sensor B No Signal” fault, relating to a missing signal from the cylinder position sensor.
Common Causes of the P1387 Code
The underlying cause depends entirely on the verified factory definition for the specific vehicle application.
For VW and Audi applications, possible causes include a failing engine control module, damaged module wiring, or an internal ECM software or hardware fault.
For Ford and Mazda applications, causes may involve a failing VCT solenoid, damaged solenoid wiring, poor electrical connections, or oil sludge clogging the solenoid screen.
For Honda and Acura applications, causes can include a failing cylinder position sensor, damaged sensor wiring, or a poor connection at the sensor harness.
Symptoms Associated With P1387
Symptoms vary depending on the underlying system fault and the vehicle manufacturer.
On VW and Audi applications with an altitude sensor fault, symptoms may include poor engine performance, reduced fuel efficiency, and an illuminated Check Engine Light.
On Ford and Mazda applications with a VCT solenoid fault, symptoms can include rough idling, engine shaking, reduced power, and hesitation during acceleration.
On Honda and Acura applications, symptoms may include a no-start condition, severe engine misfires, or stalling.
Diagnosing the P1387 Trouble Code
Diagnosis must begin by confirming the exact factory definition for the specific make, model, and year.
For VW and Audi applications, technicians inspect the ECM wiring and grounds, verify the barometric pressure sensor data with a scan tool, and test the ECM internal circuits.
For Ford and Mazda applications, technicians test the VCT solenoid resistance, inspect the solenoid screen for oil sludge, and verify the control circuit for opens or shorts.
For Honda and Acura applications, technicians test the cylinder position sensor signal and inspect the wiring harness for damage.
Repairing the P1387 Issue
Repairs must follow confirmed diagnosis based on the specific vehicle application.
If an ECM internal fault is confirmed on a VW or Audi application, the engine control module may need to be replaced or professionally reprogrammed.
If a VCT solenoid or circuit fault is confirmed on a Ford or Mazda application, the solenoid must be replaced, the screen cleaned, or the damaged wiring repaired.
If a cylinder position sensor fault is confirmed on a Honda or Acura application, the sensor or damaged wiring must be replaced or repaired.
Cost Considerations for P1387 Repairs
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Replacing a VCT solenoid or cylinder position sensor may require minimal labor depending on accessibility.
Conversely, replacing and programming an engine control module requires specialized equipment and significant labor.
Prevention Strategies for Future Occurrences
Some electrical and mechanical failures cannot be reliably prevented.
For applications using variable cam timing, performing regular oil changes with the correct oil viscosity helps prevent sludge from clogging the VCT solenoid screens.
Inspecting exposed wiring harnesses for chafing or heat damage can help prevent intermittent circuit faults in the sensor or solenoid systems.
Troubleshooting Tips and Best Practices
Never assume P1387 is a universal altitude sensor or VCT code. Always verify the exact definition for the specific vehicle before purchasing parts.
Do not ignore related codes. A VCT solenoid fault may appear alongside other camshaft timing codes, while an altitude sensor fault may appear alongside MAP sensor codes.
Check for technical service bulletins applicable to your exact vehicle application, as manufacturers frequently release updated solenoids or revised ECM software for recurring faults.
More OBD-II Codes
| P1386 | P1388 | P0010 | P0300 |
| P1382 | P1389 | P0011 | P0171 |
| P1381 | P1390 | P0012 | P0174 |
| P1380 | P1391 | P0014 | P0420 |
| P1378 | P1392 | P0430 | P0101 |
| P1377 | P1393 | P0340 | P0335 |
Frequently Asked Questions
Is P1387 a generic or manufacturer-specific code?
No. P1387 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 P1387 code?
It depends on the application. If P1387 indicates an ECM internal fault, performance may be reduced. If it is a VCT or cylinder position fault, the engine may stall or misfire.
Will disconnecting the battery clear the P1387 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 low oil cause a P1387 code?
On Ford and Mazda applications monitoring the VCT system, low or degraded engine oil can prevent the variable cam timing system from operating correctly and clog the solenoid screen.
Does P1387 always mean the ECM is bad?
No. While an internal ECM fault is a cause on VW and Audi applications, the code can also indicate a failing VCT solenoid, damaged wiring, or a bad cylinder position sensor.
What Should You Do About the P1387 Code?
Confirm the exact factory definition and diagnostic procedure for your specific vehicle application. Because P1387 is manufacturer-specific, identifying whether it relates to an altitude sensor, a VCT solenoid, or a cylinder position sensor 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.
