Glow Plug Light (Diesel)

What it means

On diesel engines this light comes on when the key is turned to show the glow plugs are preheating the combustion chambers, and you should wait for it to go out before cranking. If it flashes while driving, it usually indicates an engine or preheating fault.

Symptoms4

• The light comes on for a few seconds and goes out at every start, which is normal.
• The light flashes while driving.
• Hard starting on cold mornings.
• White smoke right after starting.

Possible causes4

• One or more failed glow plugs.
• A faulty glow plug relay or control module.
• A faulty engine temperature sensor.
• Other engine faults that some manufacturers report through the same light.

How to diagnose and fix5

1. Wait for the light to go out before cranking every time.
2. If it flashes while driving, reduce load and drive gently to a workshop.
3. Read the fault code to identify the affected plug or circuit.
4. Measure each glow plug resistance and replace any that fail.
5. Check the glow plug relay and its connections.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

A glow plug or relay is usually cheap to moderate, rising somewhat if a plug is seized and hard to remove.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.

Frequently asked questions