P0670 means Glow Plug Module Control Circuit. The computer has detected a fault in the circuit it uses to command the glow plug control module. 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 P0670 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.
P0670 symptoms
- Hard cold starts
- Glow plug light behaving oddly
- Check engine light
Common causes of P0670
- Wiring fault between the computer and the glow plug module
- Failed glow plug module
- Poor ground or power to the module
How to diagnose P0670
- Check the module’s power and ground
- Check the command circuit for opens or shorts
- Read glow plug module codes with a capable scan tool
Can you drive with P0670?
Yes in warm weather.
P0670 tips
Glow plug modules are often mounted in hot or wet locations; corrosion at the connector is a common cause.
Will P0670 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 P0670 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 |
| P0683 | Glow Plug Control Module to PCM Communication 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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