Glow Plug Diagnostic Signal Communication Fault
The P0683 code indicates a communication fault between the glow plug control module and the engine control module (ECM) via the glow plug diagnostic signal circuit. This circuit is used to monitor the status of the glow plugs and relay diagnostic information. A fault can prevent proper glow plug operation, leading to hard starting, especially in cold weather, and increased emissions.
1. Most Common Causes
- Faulty glow plug control module
- Open or shorted wiring in the diagnostic signal circuit
- Corroded or loose electrical connectors
- Failed ECM (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Excessive smoke from exhaust on startup
- Reduced engine performance
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Visually inspect the glow plug control module connector and wiring for damage or corrosion.
Step 3: Test the diagnostic signal circuit for continuity and shorts using a multimeter.
Step 4: Check the glow plug control module power and ground supplies.
Step 5: If all else is okay, replace the glow plug control module.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances, especially in cold weather, as the glow plugs may not function properly, leading to hard starting and potential stalling. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on the root cause. Replacing the glow plug control module can cost $100-$300 including parts and labor.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.