P0683

Symptoms

• Complete failure of the glow plug system
• Inability to start a diesel engine in cold weather
• Check Engine Light
• The glow plug indicator is constantly on
• Loss of communication with GPCM in the diagnostic scanner

Causes

• Damage to the wiring of the communication circuit between the GPCM and the ECU
• Oxidation or breakage of module connectors
• GPCM module malfunction
• GPCM power or ground fault
• Internal ECU fault

How to Fix

1. Read OBD-II codes and check for lost communication codes
2. Check power and ground of GPCM module
3. Inspect the wiring of the communication circuit between the GPCM and the ECU
4. Measure resistance and voltage in the communication circuit
5. Check the connectors of both modules for oxidation and damage.
6. Replace GPCM or ECU if internal fault is confirmed

Related codes

Error P0683 by Vehicle Brand