P0381 — Glow Plug/Heater Circuit "A" Malfunction
Drive with caution — fix soon.
What P0381 means
This code indicates a malfunction in the glow plug heater circuit "A," which warms the engine to help it start in cold conditions. It's usually caused by a bad glow plug control module, a faulty glow plug, or damaged wiring in the circuit. It's a common diesel code and is normally repaired by fixing the circuit or replacing the failed glow plug or controller.
Common symptoms
- Check engine light is on
- Hard or extended cranking when cold
- Glow plug indicator light stays on or flashes
- White exhaust smoke on a cold start
- Rough idle until the engine warms up
Common causes
- Failed glow plug control module
- One or more bad glow plugs
- Corroded or broken wiring in the glow plug circuit
- Blown glow plug system fuse
- Faulty relay supplying the glow plugs
Typical repair cost
$150 – $700
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0381 code?
Yes, in most cases, since the engine usually still runs fine once started. The main downside is harder cold starts, so plan to fix it before winter or before the cranking gets noticeably worse.
How much does it cost to fix a P0381 code?
Repairs typically run $150 to $700. Replacing a single glow plug or fixing wiring is cheaper, while a full set of glow plugs or a control module is more expensive.
Is a P0381 code serious?
It's moderate. It doesn't usually harm the engine, but a failing glow plug system can eventually leave you unable to start, especially in cold climates.
Will a P0381 code cause white smoke when I start the car?
It can. Glow plugs help fully ignite the fuel on a cold start, and when they're weak some fuel burns incompletely, producing white smoke that usually clears as the engine warms up.