Engine
What Does the Glow Plug Warning Light Mean?
The glow plug light indicates that the pre-heating system is active, but if it flashes or stays on, there may be a fault with the glow plugs or control module.
Diesel engines use glow plugs to heat the combustion chambers for cold starting. When you turn the ignition, the glow plug light illuminates briefly while the plugs warm up. If the light flashes or stays on longer than usual, one or more glow plugs may have failed, or the glow plug control module could be faulty. Symptoms include hard starting in cold weather, white smoke on start-up, and rough idling until the engine reaches operating temperature. Most glow plugs are relatively inexpensive to replace, but access can be difficult on some engines.
Key takeaways
- Flashing glow plug light indicates a fault in the pre-heating system
- Hard cold starting and white smoke are common symptoms of failed glow plugs
- Faulty glow plugs can cause a diesel engine to fail an MOT emissions test
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