P0687 OBD II Trouble Code ECM/PCM Power Relay Control Circuit High

Symptoms of P0687 OBD II Trouble Code

  • The alternator may be overcharging
  • Faulty PCM power relay
  • A faulty ignition switch
  • Shorted wiring or wiring connectors

Common Causes of P0687 OBD II Trouble Code

  • If there is a charging lamp illuminated or an alternator overcharging code present, diagnose and repair that code (or condition) before the P0687
  • Check for alternator overcharging first
  • Swap only identical (matching numbers) relays for testing purposes
  • Return relays to their original position, replacing the defective relay with a new relay