P0684 - Glow Plug Control Module (GPCM) to Powertrain Control Module (PCM) Communication Circuit Range/Performance
Description: During the glow plug system check, the PCM enables the GPCM and monitors the GPCM/PCM communication circuit for a response. The DTC sets when the PCM stops receiving messages or receives an error message from the GPCM over the communication circuit.
Possible Causes:
• GPCM/PCM communication circuit open in the harness
• GPCM/PCM communication circuit short to ground in the harness
• GPCM/PCM communication circuit short to voltage in the harness
Diagnostic Aids: This DTC may be set as a result of the concern with GPCM control circuit. Diagnose DTC P0670 before diagnosing DTC P0684
