Engine warning light

Red or amber: what the colour means

Dashboard lights follow a simple colour code. Check your handbook for your car’s symbols, but as a rule:

• Red: a serious problem. Stop as soon as it is safe to do so and switch the engine off.
• Amber or yellow: something needs checking soon. You can usually keep driving carefully to a garage.
• Green or blue: information only, such as headlights or cruise control.

Common red warning lights

• Oil pressure (an oil can): stop straight away. Driving without oil pressure can wreck the engine in minutes.
• Coolant temperature (a thermometer): the engine is overheating. Stop, let it cool, and never open a hot coolant cap.
• Brake system (a circle with an exclamation mark): check the handbrake is off. If it stays on, the brake fluid may be low. Don’t drive on.
• Battery or charging (a battery): the alternator isn’t charging. The car will run until the battery is flat, so head somewhere safe and get it checked.

Common amber warning lights

• Engine management (an engine outline): the engine computer has found a fault. If it’s flashing, the engine is probably misfiring: reduce speed and get it checked straight away, as driving on can damage the catalytic converter.
• ABS: your normal brakes still work, but anti-lock braking may not. Drive gently and get it checked.
• Airbag (SRS): the airbags may not deploy in a crash. Get it checked soon.
• Tyre pressure: one or more tyres may be low. Check pressures and look for a puncture.
• DPF (diesels): the diesel particulate filter is getting blocked. A steady run at motorway speed often clears it. If not, it needs looking at.
• Glow plug (diesels, a coil symbol): normal briefly when starting. If it stays on or flashes while driving, there’s a fault to check.

Can I keep driving?

With a red light, no: stop safely and get help. With a steady amber light the car is usually safe to drive carefully to a garage, but don’t ignore it. Small faults can become expensive ones. If the car feels different (loss of power, juddering, strange noises or smells), treat it as urgent.

Warning lights and the MOT

An engine management, ABS or airbag light that stays on is an MOT failure, and so is a tyre pressure warning light on cars first used from 1 January 2012. Get warning lights sorted before your MOT.

What a garage will do

A garage or mobile mechanic will plug a diagnostic tool into the car’s computer and read the fault codes. A code says where the fault was detected, not always what caused it, so a good mechanic will test the suspect parts before replacing anything. Ask what they found and what it will cost before agreeing to repairs. Garages set their own prices.

Frequently asked questions

Why is my engine warning light on but the car drives fine?

Many engine faults, such as a faulty sensor or an emissions problem, don’t change how the car feels at first. Get it read soon so a small fault doesn’t become a bigger one.

Will the light go off by itself?

Sometimes, if the fault was temporary. The fault code is usually still stored, so it’s worth having it read.

Can a mobile mechanic read warning light codes?

Yes. Many mobile mechanics carry diagnostic equipment and can read codes where the car is parked.

What does a flashing engine light mean?

Usually an engine misfire. Reduce speed, avoid hard acceleration and get it checked straight away.