P0683 means Glow Plug Control Module to PCM Communication Circuit. The engine computer and the glow plug control module are not communicating correctly, so the computer cannot confirm the glow plug status. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0683 means
Many diesel engines use glow plugs to heat each combustion chamber so the engine can start in cold weather; others, including Cummins engines in Ram pickups, use an intake air heater instead. A glow plug control module or relay switches the plugs on before and after a cold start and monitors each circuit. Glow plug codes usually point to one failed plug, its wiring, or the controller that feeds them all, and the symptoms show up mainly in cold weather.
P0683 symptoms
- Hard cold starts
- Glow plug light on
- Check engine light
Common causes of P0683
- Failed glow plug module, often mounted where it sees heat and moisture
- Corroded connector
- Wiring fault in the communication circuit
How to diagnose P0683
- Inspect the module connector for corrosion
- Check module power and ground
- Check the communication circuit
Can you drive with P0683?
Yes in warm weather.
P0683 tips
The glow plug module and its connector are frequent failure points on some diesel pickups; inspect for corrosion before replacing the module.
Will P0683 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0683 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0380 | Glow Plug/Heater Circuit A |
| P0670 | Glow Plug Module Control Circuit |
| P0671 | Cylinder 1 Glow Plug Circuit |
Guides that help
When it is more than a sensor
Glow plug faults are almost always fixed with plugs, wiring or the controller rather than major parts. If hard starting turns out to be low compression or injector problems, see how long diesel engines last and compare replacement engines on our Cummins engines page.
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