P0688 OBD II Trouble Code ECM/PCM Power Relay Sense Circuit Open

How to easily diagnose, repair, and info on causes of a P0688 trouble code that indicates an open state of the ECM/PCM power relay sense circuit.

Symptoms of P0688 OBD II Trouble Code

  • Delayed or no start
  • Electrical accessories may be inoperative
  • Engine drivability issues

Common Causes of P0688 OBD II Trouble Code

  • Defective PCM power relay
  • Blown fuse or fusible link
  • Open or shorted circuit between the power relay and the PCM

Severity of P0688 OBD II Trouble Code

A P0688 should be categorized as severe and addressed accordingly. It may result in a a no start condition and/or a variety of drivability issues.