Glow Plug Warning (Diesel)
Diesel engines only: glow plugs are preheating (normal at startup) — or a plug has failed if the light stays on or flashes.
What it means
On diesels, this coil symbol lights at key-on while the glow plugs heat the cylinders — wait for it to go out before cranking in cold weather. If it stays lit or flashes while driving, one or more glow plugs or the control module has failed.
Can you keep driving?
Yes with a steady light, though cold starts will be harder and rough. A flashing glow plug light on many diesels indicates an engine-management fault that may put the car in limp mode — get it scanned soon.
What to do now
- 1
At startup, wait for the light to go out before cranking, especially in the cold.
- 2
If it stays on or flashes, have the codes read — on some cars this overlaps with the engine-management system.
- 3
Replace failed glow plugs as a set where practical; a seized plug can break off in the head, so use a shop if plugs are old.
Likely causes
- • Normal preheat cycle (light goes out in a few seconds)
- • Burned-out glow plug
- • Faulty glow plug relay or control module
- • Wiring fault
Typical fix cost
$100–$400 for a set of glow plugs; $80–$200 for a relay
Ranges reflect mainstream US parts-and-labor pricing; your vehicle and region will vary.