P0380 means Glow Plug/Heater Circuit A. The computer has detected a fault in glow plug or heater circuit A, which can mean a failed relay, controller, wiring or plugs. 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 P0380 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.
P0380 symptoms
- Hard starting in cold weather
- White smoke and rough running after a cold start
- Glow plug or wait-to-start light acting oddly
Common causes of P0380
- Failed glow plug relay or controller
- Blown fuse or fusible link
- Wiring fault
- Failed glow plugs
How to diagnose P0380
- Check the fuse and relay or controller
- Check for voltage at the plug feed during the glow cycle
- Measure each plug’s resistance
Can you drive with P0380?
Yes in warm weather; cold starts will be difficult.
P0380 tips
Check the glow plug fuse and relay first; they feed every plug, so a single failure affects all cylinders.
Will P0380 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 P0380 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 |
|---|---|
| P0670 | Glow Plug Module Control Circuit |
| P0671 | Cylinder 1 Glow Plug Circuit |
| P0683 | Glow Plug Control Module to PCM Communication 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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