Glow Plug Control Module Communication Failure
The P0683 code indicates a communication fault between the Glow Plug Control Module (GPCM) and the Powertrain Control Module (PCM). This typically occurs when the PCM does not receive the expected signal from the GPCM over the dedicated communication circuit. The GPCM controls the glow plugs for cold start assistance in diesel engines. A failure in this circuit can prevent the glow plugs from operating, leading to hard starting in cold weather.
01. Most Common Causes
- Faulty Glow Plug Control Module
- Open or shorted communication circuit between GPCM and PCM
- Corroded or loose connectors at GPCM or PCM
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Excessive white smoke on startup
- Possible glow plug warning light on dashboard
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Visually inspect the GPCM and PCM connectors for corrosion, damage, or loose pins.
Step 3: Test the communication circuit between GPCM and PCM for continuity and shorts using a multimeter.
Step 4: Check power and ground supplies to the GPCM.
Step 5: If circuit tests pass, replace the GPCM and clear codes.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code, especially in cold weather, as the glow plugs may not function, leading to hard starting and potential stalling. In warmer climates, the vehicle may start but could still have drivability issues.
How much does it cost to fix?▼
The cost to diagnose and repair P0683 typically ranges from $50 to $150 for diagnosis, plus parts and labor. Replacing the GPCM can cost $200-$400 total, depending on the vehicle.