Car dashboard warning lights

The next step

Already had the codes read?

A symbol tells you which system is unhappy. The fault code stored behind it names the specific check that failed, which is where a diagnosis actually starts. If somebody has read yours, look it up.

Common questions

Which dashboard warning lights fail an MOT?

Eight tell-tales are listed defects in the MOT inspection manual: the engine management lamp, the brake system warning device, the airbag or SRS lamp, the stability control lamp, the tyre pressure monitoring lamp, the electric power steering lamp, the electronic parking brake lamp, and the mandatory tell-tale for main beam and rear fog. If any of these is illuminated, the car fails regardless of how it drives. Together they account for 674,636 recorded failures in the DVSA data behind this site, with the engine management lamp alone responsible for 371,859.

What do the colours of dashboard warning lights mean?

Under ISO 2575, red is reserved for hazards and for faults where continuing could injure somebody or destroy something expensive, amber means a system has reported a malfunction or needs attention, green confirms something is switched on and working, and blue is almost exclusively main beam. There are a few exceptions worth knowing: the hazard tell-tale is red but means nothing is wrong, and the red battery charge lamp is one where stopping can be the wrong move, because the car may not restart.

Can I drive with a warning light on?

It depends entirely on which one. Red oil pressure and coolant temperature lamps mean stop immediately, because an engine can be destroyed in under a minute. Most amber lamps mean the car is driveable but the fault will not clear itself, and several of them will fail an MOT. Green and blue lamps are simply confirming something is switched on. Look up the specific symbol rather than going by colour alone.

Will a warning light go off by itself?

Some will. A diesel particulate filter lamp usually clears after a longer, faster drive, and a tyre pressure lamp clears once the tyres are correctly inflated and the system has relearned. Most others stay on until the fault is repaired and the code cleared. A lamp that goes out on its own without anything being fixed often means an intermittent fault, which will come back, and the stored code will still be readable.

Can a garage clear a warning light to get a car through an MOT?

Clearing the code without fixing the fault rarely works and often makes things worse. Clearing it also resets the on-board readiness monitors, and a tester can see they have not completed. On many cars the emissions check cannot be finished until the monitors have run, which needs a drive cycle of up to a hundred miles, so the car fails on an incomplete emissions test instead of on the lamp.