Glow Plug Control Module to PCM Communication Circuit
The PCM can't communicate with the glow plug control module, like a radio losing its signal to the speaker. This prevents proper glow plug operation in diesel engines, affecting cold starts and engine performance.
The PCM monitors the communication signal between itself and the glow plug control module via CAN or serial bus protocol. It checks for valid message transmission, response acknowledgment, and signal integrity at regular intervals during engine operation and startup cycles.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Communication Signal Validity | Valid CAN/serial messages received within 100ms intervals | No response or corrupted messages for >500ms |
| Module Response Time | Glow plug module responds within 50-100ms | Response timeout or delayed >150ms |
Code P0683 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0683 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.