Diesel preheating warning light: meaning and what to do

Diesel preheating

The exact symbol can vary between makes and models. Also check the message displayed by the vehicle.

How urgent is it?

May be normal before starting; flashing or remaining lit after starting requires checks.

How to recognise it

Coil or spring-shaped symbol.

What it can mean

At ignition, it can indicate normal preheating. Illumination or flashing while driving can mean something else; it does not alone prove failed glow plugs.

What to do

Wait for it to go out before starting if the handbook requires it. For a warning while driving, read the message and arrange diagnostics.

Before clearing the light or codes

Photograph the dashboard message and save all codes, the reporting module, fault status and freeze-frame data. Clearing can remove useful evidence without repairing the cause.

From warning light to inspection

A warning light can have many causes. The example codes below have NOT been scanned from your vehicle.