P0683Powertrain
Powertrain · SAE
Glow Plug Module to PCM Communication — Circuit
Meaning
The glow plug control module (GSC) is unable to communicate correctly with the powertrain control module (PCM/ECM) via the communication bus. Active glow plug control and diagnostics are compromised.
Common causes
- Damaged or broken communication wiring between the GSC and PCM
- Defective or improperly powered GSC module
- PCM/ECM fault preventing communication
- Short circuit on the communication line (CAN or dedicated line)
- Incorrect software update or misconfiguration of the GSC
Symptoms
- Check engine light on
- No active glow plug control (hard cold start)
- No glow plug data available on scan tool
- Possible accompanying CAN communication codes
- Pre-heat system completely inactive
Severity
Moderate to high: without communication the pre-heat system does not operate; in cold climates the engine may fail to start, and irregular combustion can cause engine damage.
What to do
- Check supply voltage (12 V) and ground connection at the GSC module
- Inspect wiring between GSC and PCM for shorts, open circuits, or connector oxidation
- Check for accompanying CAN fault codes and diagnose the communication bus
- Substitute the GSC module with a known-good unit to rule out the component
- Reflash or reprogram the GSC if directed by the manufacturer procedure