Amber · Info / system on
Glow plug (diesel) warning light — what it means
Normal wait-to-start on many diesels; stays on = fault. On most UK cars this shows as a amber tell-tale. Urgency: Info / system on. Symbols vary by brand — confirm the exact icon in your handbook.
Also called: glow, coil, preheat
What it means
Normal wait-to-start on many diesels; stays on = fault.
What to do first: Wait for it to extinguish before cranking. If it stays on while driving, scan soon.
Common causes
- A genuine glow plug (diesel) system fault
- A failed sensor or switch reporting a false warning
- Low voltage after a weak 12V battery (can set multiple lamps)
- Recent work (battery change, wheels, sensors) that needs a reset or calibration
Step-by-step
- 1Wait for it to extinguish before cranking. If it stays on while driving, scan soon.
- 2Photograph the light and any message-centre text for the garage or breakdown operator.
- 3Note whether the car feels normal — power loss, smoke, smells or strange noises change the priority.
- 4Avoid clearing codes repeatedly without fixing the cause; the fault will return and can fail an MOT.
MOT note
Informational lights (green/blue) are not faults. Amber faults should still be diagnosed promptly.
FAQs
- What does the Glow plug (diesel) warning light mean?
- Normal wait-to-start on many diesels; stays on = fault. Wait for it to extinguish before cranking. If it stays on while driving, scan soon.
- Can I drive with the Glow plug (diesel) light on?
- Usually informational — confirm in the handbook that it is not also used as a fault lamp on your model.
Related
Other warning lights
Icons from Wikimedia Commons dashboard tell-tales / ISO 7000. Manufacturer artwork varies — your handbook wins.