Symptoms of P0686 OBD II Trouble Code
- A defective ignition switch
- Faulty PCM power relay
- A blown fusible link or fuse
- Loose or corroded battery cable ends
- Corroded or damaged wiring or wiring connectors (especially near the PCM relay)
- Partially or totally disconnected electrical terminal at the ignition switch
Common Causes of P0686 OBD II Trouble Code
- If the service engine soon lamp fails to illuminate when the ignition switch is placed in the KOEO position, suspect a defective PCM power relay
- Swap identical (matching numbers) relays for testing purposes
- Test alternator output to make sure that it is sufficient