Glow Plug Control Module to PCM Communication Circuit
The PCM (Powertrain Control Module) has detected a communication failure between itself and the glow plug control module. This code typically appears on diesel vehicles where the glow plug system is essential for cold starting and combustion efficiency.
What You Might Notice
- Check Engine Light illuminated
- Difficulty starting the engine, especially in cold weather
- Engine misfire or rough idle until engine warms up
- Reduced fuel efficiency
- Possible loss of glow plug function
Most Common Causes
- 1
Faulty glow plug control module
The glow plug control module has failed internally or lost its ability to communicate with the PCM via the CAN bus or dedicated communication circuit.
- 2
Damaged wiring or connectors
Corroded, loose, or broken wires and connectors in the communication circuit between the PCM and glow plug control module prevent proper signal transmission.
- 3
PCM software issues
Outdated or corrupted PCM firmware may fail to properly recognize or communicate with the glow plug control module, requiring a software update or reflash.
- 4
Failed individual glow plugs
While one or two failed glow plugs may not trigger the code alone, multiple failures can cause the control module to report communication loss to the PCM.
How to Diagnose It
- 1
Check Faulty glow plug control module — The glow plug control module has failed internally or lost its ability to communicate with the PCM via the CAN bus or dedicated communication circuit.
- 2
Check Damaged wiring or connectors — Corroded, loose, or broken wires and connectors in the communication circuit between the PCM and glow plug control module prevent proper signal transmission.
- 3
Check PCM software issues — Outdated or corrupted PCM firmware may fail to properly recognize or communicate with the glow plug control module, requiring a software update or reflash.
- 4
Check Failed individual glow plugs — While one or two failed glow plugs may not trigger the code alone, multiple failures can cause the control module to report communication loss to the PCM.
How to Fix It
- 1
Inspect and repair wiring harness
Check all wiring and connectors between the PCM and glow plug control module for corrosion, loose connections, or damage. Clean connectors with electrical contact cleaner and ensure proper seating.
- 2
Replace glow plug control module
If wiring inspection reveals no issues, the glow plug control module has likely failed internally and must be replaced with a new or remanufactured unit.
- 3
Update or reflash PCM software
Contact the vehicle manufacturer or use a professional diagnostic scanner to determine if a PCM software update is available. Perform a complete reflash if outdated firmware is detected.
- 4
Test and replace glow plugs
Use a multimeter to test each glow plug for continuity and proper resistance. Replace any glow plugs that are open or reading out-of-specification.
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