The P0687 trouble code is an OBD-II diagnostic code indicating a high voltage condition in the Engine Control Module (ECM) or Powertrain Control Module (PCM) power relay control circuit. This code is triggered when the PCM detects an abnormal voltage reading from the power relay that supplies power to it. Understanding this code is crucial for vehicle owners and DIY mechanics, as it can lead to significant issues if not addressed promptly.
| P0687 Code Meaning | P0687 Code Common Causes |
|---|---|
| ECM/PCM Power Relay Control Circuit High | Overcharging alternator |
| High voltage detected by PCM | Faulty ignition switch |
| Potential damage to PCM | Defective PCM power relay |
| Possible no-start condition | Shorted or open circuit in wiring |
| Check Engine Light illumination | Corroded or damaged connectors |
Symptoms of P0687 Code
The symptoms associated with the P0687 trouble code can vary based on the severity of the underlying issue. Common symptoms include:
- Check Engine Light: The most immediate indication that something is wrong.
- Engine Hard to Start: Difficulty in starting the engine, especially in cold weather.
- Engine Stalling: The engine may stall unexpectedly during operation.
- Decreased Power: Noticeable reduction in engine performance and acceleration.
- Other Codes: Additional trouble codes may be present, indicating related issues.
Technical Explanation of P0687
The P0687 code indicates that the PCM has detected a high voltage condition in its power relay control circuit. The ECM/PCM relies on a stable voltage supply to function correctly. If the voltage exceeds normal levels, it can lead to various operational issues, including failure to start and potential damage to the PCM itself.
Step-by-Step Diagnosis
Diagnosing the P0687 code involves several steps:
- Retrieve Codes: Use an OBD-II scanner to confirm the presence of the P0687 code and any other related codes.
- Visual Inspection: Check for damaged wiring, corroded connectors, or any visible signs of wear between the battery and the PCM.
- Test Voltage: Using a digital volt/ohmmeter (DVOM), measure the voltage at the power relay control circuit. Ensure it falls within manufacturer specifications.
- Check Relay Functionality: Test the PCM power relay for proper operation. If it fails to click when energized, it may need replacement.
- Inspect Alternator Output: Check if the alternator is overcharging, which could lead to excessive voltage being sent to the PCM.
- Examine Ignition Switch: A faulty ignition switch can cause erratic voltage readings; test its functionality as well.
- Clear Codes and Test Drive: After repairs, clear any stored codes and take the vehicle for a test drive to see if the P0687 code reappears.
Solution Methods for P0687
Addressing a P0687 code typically involves several repair options:
Repairing or Replacing Components
- Alternator Repair/Replacement: If overcharging is detected, repair or replace the alternator as needed.
- Ignition Switch Replacement: If found faulty during testing, replacing the ignition switch can resolve erratic voltage issues.
- PCM Power Relay Replacement: A defective relay must be replaced to restore proper function to the power supply circuit.
- Wiring Repairs: Any damaged or corroded wiring should be repaired or replaced to ensure a stable connection between components.
Cost Estimates
The cost of repairs can vary significantly based on labor rates and parts prices:
- Alternator Replacement: $300 – $800 depending on vehicle make and model.
- Ignition Switch Replacement: $100 – $300 including parts and labor.
- PCM Power Relay Replacement: $50 – $150 for parts; labor costs may vary.
- Wiring Repairs: Costs depend on extent of damage; minor repairs could be under $100 while extensive rewiring could exceed $500.
Warnings and Recommendations
It is crucial not to ignore a P0687 code. Continuing to operate your vehicle with this issue could lead to severe damage to your PCM, potentially requiring costly replacement.
- Always perform repairs promptly after diagnosing a trouble code.
- If you are unsure about any steps in diagnosing or repairing this issue, consult with a professional mechanic.
Frequently Asked Questions About P0687
- What does P0687 mean?
The P0687 code indicates that there is a high voltage condition in the ECM/PCM power relay control circuit. - Can I drive my car with a P0687 code?
While you may be able to drive your vehicle temporarily, it is not advisable as it can lead to further damage. - How serious is a P0687 code?
This code should be addressed urgently as it can indicate potential damage to critical engine control components. - What tools do I need to diagnose a P0687?
A suitable OBD-II scanner and a digital volt/ohmmeter are essential for accurate diagnosis. - Can I fix a P0687 code myself?
If you have basic mechanical skills and tools, you can perform some diagnostics and repairs; however, professional help may be needed for complex issues. - What are common causes of the P0687 code?
Common causes include overcharging alternators, faulty ignition switches, defective power relays, and damaged wiring. - Will clearing the code fix my car?
No, simply clearing the code will not fix underlying issues; proper diagnosis and repair are necessary. - How much does it cost to repair a P0687?
The cost varies widely but could range from $100 for minor fixes up to $800 for major component replacements.
In conclusion, understanding and addressing the P0687 trouble code is essential for maintaining your vehicle’s performance and preventing costly repairs down the line. By following proper diagnostic procedures and addressing any identified issues promptly, vehicle owners can ensure their vehicles remain safe and reliable on the road.