The P0687 trouble code is an OBD-II diagnostic trouble code that indicates a high voltage condition in the ECM (Engine Control Module) or PCM (Powertrain Control Module) power relay control circuit. This code is triggered when the PCM detects that the voltage supplied to it through the power relay exceeds normal operating levels. The P0687 code can lead to various symptoms, including difficulty starting the engine, reduced engine performance, and illumination of the Check Engine Light. Understanding this code is crucial for vehicle owners and DIY mechanics to ensure proper diagnosis and repair.
| P0687 Code Meaning | P0687 Code Common Causes |
|---|---|
| High voltage detected in the ECM/PCM power relay control circuit | Faulty PCM power relay |
| Potential damage to the PCM due to excessive voltage | Overcharging alternator |
| Possible engine performance issues | Faulty ignition switch |
| Check Engine Light illumination | Shorted or open wiring in the power relay circuit |
| No-start condition in some cases | Corroded or loose electrical connections |
Symptoms of P0687 Code
When dealing with a P0687 trouble code, several symptoms may manifest, which can help diagnose the underlying issue:
- Check Engine Light: The most common symptom is the illumination of the Check Engine Light on the dashboard.
- Difficulty Starting: In some cases, the vehicle may experience difficulty starting or may not start at all.
- Reduced Engine Power: Drivers may notice a decrease in engine power and acceleration.
- Engine Misfiring: The engine may misfire or hesitate during operation.
- Stalling: The vehicle may stall unexpectedly while driving.
Understanding these symptoms is crucial for timely diagnosis and repair, as prolonged issues can lead to further damage to the PCM.
Technical Explanation of P0687 Code
The P0687 code specifically relates to a high voltage condition detected by the PCM in the power relay control circuit. The power relay is responsible for supplying battery voltage to the PCM when the ignition is turned on.
How It Works
- Power Supply: The battery provides voltage to the power relay.
- Relay Activation: When the ignition switch is turned on, a small coil inside the relay activates, closing contacts that allow battery voltage to flow to the PCM.
- Voltage Monitoring: The PCM continuously monitors this voltage supply. If it detects a voltage that exceeds its specified range (typically above 16 volts), it will trigger the P0687 code.
This high voltage can be caused by several factors, including a malfunctioning alternator that overcharges or issues within the wiring harness itself.
Step-by-Step Diagnosis of P0687 Code
Diagnosing a P0687 trouble code involves several steps to identify and rectify the underlying issue:
- Initial Scan: Use an OBD-II scanner to confirm that P0687 is present along with any other related codes.
- Visual Inspection:
- Inspect wiring harnesses and connectors for damage, corrosion, or loose connections.
- Check battery terminals and cables for corrosion or looseness.
- Test Power Relay:
- Locate the PCM power relay and listen for an audible click when turning on the ignition.
- Use a multimeter to test for proper operation of the relay.
- Check Voltage Levels:
- Measure voltage at the power relay control circuit using a multimeter.
- Ensure that voltage levels are within acceptable limits (typically between 12-14 volts).
- Inspect Alternator Output:
- Test the alternator to ensure it is not overcharging.
- A properly functioning alternator should not exceed 14.5 volts during operation.
- Examine Ignition Switch:
- Check if there are any faults with the ignition switch that could affect voltage supply.
- Clear Codes and Test Drive:
- After making repairs, clear any stored codes from the PCM and perform a test drive to verify if P0687 returns.
Solution Methods for P0687 Code
Resolving a P0687 trouble code may involve several repair methods depending on what has been diagnosed:
- Replace Faulty Relay: If testing reveals that the PCM power relay is defective, replacing it can resolve the issue.
- Repair Wiring Issues: Any damaged, corroded, or shorted wiring should be repaired or replaced as necessary.
- Check Alternator: If overcharging is detected, repair or replace components in the charging system as needed.
- Ignition Switch Replacement: If faults are found in the ignition switch, replacing it may restore proper function.
- PCM Replacement: In rare cases where all other components are functioning correctly but codes persist, consider inspecting or replacing the PCM.
Cost Estimates
The costs associated with diagnosing and repairing a P0687 code can vary widely based on location and vehicle type:
- Diagnostic Fee: $75-$150 (depending on labor rates)
- Relay Replacement: $30-$100 (parts only)
- Wiring Repairs: $50-$200 (depending on extent of damage)
- Alternator Replacement: $300-$800 (parts and labor)
- PCM Replacement: $500-$1500 (including programming)
Warnings and Recommendations
It’s important to address a P0687 trouble code promptly. Ignoring this issue can lead to severe damage to your vehicle’s PCM, potentially resulting in costly repairs down the line.
- Always ensure that repairs are performed by qualified technicians if you are unsure about any step in diagnosing or repairing your vehicle.
- Regularly check your vehicle’s electrical systems as part of routine maintenance to prevent future issues related to high voltage conditions.
Frequently Asked Questions About P0687
- What does code P0687 mean?
Code P0687 indicates a high voltage condition detected in the ECM/PCM power relay control circuit. - Can I drive my car with a P0687 code?
While it’s possible to drive with this code present, it’s not recommended as it can lead to further damage if left unresolved. - What are common symptoms of a P0687 code?
Common symptoms include Check Engine Light illumination, difficulty starting, reduced engine performance, and potential stalling. - How serious is a P0687 trouble code?
The seriousness of this code can vary; however, it requires prompt attention as excessive voltage can damage critical engine components. - What should I do first when I see this code?
Start by scanning for additional codes and performing a visual inspection of wiring and connectors. - Can I fix a P0687 code myself?
If you have automotive knowledge and tools, you may resolve simpler issues; otherwise, consult a professional mechanic. - How much does it cost to fix a P0687 code?
Costs can range from $75 for diagnostics up to $1500 for extensive repairs like replacing a PCM. - Is there any risk in ignoring this trouble code?
Yes, ignoring this code can lead to more severe electrical problems and potential failure of your vehicle’s engine control systems.
In conclusion, understanding and addressing trouble codes like P0687 is essential for maintaining vehicle health and performance. By following systematic diagnostic procedures and addressing any identified issues promptly, vehicle owners can avoid more significant problems down the road.