WOMS
P code powertrain Medium severity

P0687 ECM/PCM Power Relay Control Circuit

The OBD2 code P0687 indicates a malfunction in the ECM/PCM power relay control circuit, which affects the power supply to the engine control module (ECM) or powertrain control module (PCM)

Definition

The OBD2 code P0687 indicates a malfunction in the ECM/PCM power relay control circuit, which affects the power supply to the engine control module (ECM) or powertrain control module (PCM)

Common causes

  • Faulty ECM/PCM
  • Bad power relay
  • Open or shorted wiring in the control circuit
  • Poor ground connection
  • Blown fuse
  • Corroded connectors
  • Faulty ignition switch

Common misdiagnoses

  • Faulty ECM/PCM
  • Bad power relay
  • Wiring issues or shorts
  • Battery or charging system problems
  • Ignition switch failure
  • Faulty fuses
  • Ground connection issues
  • Sensor malfunctions

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context and help identify related issues

  2. 2. Inspect the Battery and Connections

    Ensure that the battery is fully charged and in good condition

  3. 3. Check all battery connections for corrosion, looseness, or damage

  4. 4. Examine the Fuses

    Locate and inspect the fuses related to the ECM/PCM and the power relay. Replace any blown fuses

  5. 5. Inspect the Power Relay

    Locate the ECM/PCM power relay in the fuse box or relay panel

  6. 6. Check the relay for proper operation by swapping it with a similar relay (if available) or testing it with a multimeter

  7. 7. Check Wiring and Connectors

    Inspect the wiring and connectors associated with the ECM/PCM power relay circuit for signs of damage, corrosion, or loose connections

  8. 8. Pay special attention to the wiring harness leading to the ECM/PCM

  9. 9. Test the Relay Control Circuit

    Use a multimeter to test the voltage and ground at the relay control circuit. Ensure that the ECM is sending the correct signal to activate the relay

  10. 10. Check for continuity in the circuit and look for any breaks or shorts

  11. 11. Inspect the ECM/PCM

    If all other components check out, the issue may lie within the ECM/PCM itself. Inspect for any signs of damage or water intrusion

  12. 12. If necessary, consider reprogramming or replacing the ECM/PCM

  13. 13. Check for Ground Issues

    Ensure that the ECM/PCM has a good ground connection. A poor ground can lead to various electrical issues

  14. 14. Clear Codes and Test Drive

    After performing repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  15. 15. Consult a Professional

    If the issue persists after following these steps, it may be best to consult a professional mechanic or technician for further diagnosis.Additional Tips: - Always refer to the vehicle's service manual for specific wiring diagrams and troubleshooting procedures. - Take safety precautions when working with electrical components, including disconnecting the battery when necessary. By following these steps, you should be able to identify and resolve the issue related to the P0687 code