Symptoms of P0684 OBD II Trouble Code
- The check engine light will be illuminated and the above codes will be set.
- Little if any indication will be present if only one or two glow plugs have failed. If the engine is very cold it may be a little harder to start.
- The engine may exhibit a miss until it has sufficiently warmed up.
- If more than two glow plugs are malfunctioning, the engine will be very difficult to start.
Common Causes of P0684 OBD II Trouble Code
- Open or short in the wiring from the PCM to the GPCM, to the bus bar, or from the bus bar to the glow plug.
- Failed glow plug
- Loose or corroded connections
- Failed GPCM
- Loose or corroded connections on the glow plug solenoid
- Glow plug solenoid failure
- Insufficient battery power to solenoid
- Code P0670 may accompany this code. This code points to the wiring harness from the GPCM to the solenoid as a problem.