Will my lights fail my MOT?

Monday 8th June 2026

If your MOT is coming up soon, it's important to give yourself the best chance of passing. Checking for simple, easily overlooked faults is one of the best things you can do to prepare. Between 2024 and 2025, lamps, reflectors and electrical equipment accounted for 11% of all major MOT failures. These faults are almost entirely preventable with a basic pre-MOT check. In this guide, we'll explain common light failures, covering both external lights and internal dashboard lights, and how to spot them.

External lights that can fail an MOT and how to check them

The most common issue is bulb failure, which can be easily rectified with a replacement. The worst offenders are rear lights and number plate lights, as you can't see them from the driver's seat. Checking your lights with a helper will significantly cut down the time it takes. All of the following lights will be inspected during an MOT test so take the time to check all these beforehand:.

Headlights (dipped and main beam) – Park facing a wall. Switch between dipped and full beam and confirm both illuminate on each side. Check the beam pattern on the wall. If one side aims higher or lower than the other, the alignment is off.
Sidelights/position lights – Switch on with the engine off. Walk around and confirm all four corner position lights are working.
Tail lights – Same check as sidelights; they should illuminate together. This is a common failure point, so it's worth having someone stand behind the car while you test.
Brake lights – Have someone stand behind the car while you press the pedal. Alternatively, reverse towards a reflective surface such as a garage door or wall at night. Brake lights should show a steady red light whilst the brake pedal is depressed.
Indicators – Switch to each direction in turn and walk around the car. Check the front, rear and side repeaters on both sides, and listen for irregular ticking inside the car, as an indicator that ticks too quickly can mean the circuit is failing.
Hazard lights – Same check; all indicators should flash simultaneously.
Front and rear fog lights – Rear fog lights are checked on all vehicles first used after April 1980; front fog lights must be inspected on vehicles first used after March 2018. These require the headlights to be on to activate. Confirm the dashboard warning light illuminates and check the lens at the rear is lit. Rear fog lights should be red and front fog lights should be white in colour.
Reverse lights – Select reverse with the engine running and confirm the white light activates at the rear.
Number plate lights – Switch on the headlights to check the front number plate is clearly illuminated and check the light above the rear number plate is also illuminated . This one is easily missed.
Daytime running lights – Start the engine and check whether the daytime running lights come on automatically. On some vehicles they switch off when the headlights are activated. Check your vehicle's handbook for the correct behaviour.

What dashboard lights can fail an MOT?

Every warning light should come on briefly at ignition and then go out. Any light that stays on, or fails to come on at all, is a red flag for the MOT tester. If dashboard lights stay on, get them checked before your MOT. Any dashboard warning light that remains on and indicates a serious safety or emissions issue will cause your vehicle to automatically fail its MOT test . These include the following:

Engine management light – A red engine management light is an automatic fail with no exceptions. Causes can range from a loose fuel cap to a serious engine or emissions fault. Get it diagnosed before the test.
ABS warning light – An automatic fail if it stays illuminated, as it indicates a fault with the anti-lock braking system.
Brake system warning light – An automatic fail. It can indicate low brake fluid, a pressure imbalance or a handbrake sensor fault. Check the simplest solution first: the brake fluid. If that's fine, book in for further diagnostics.
Airbag/SRS (Supplemental Restraint System) warning light – An automatic fail. This means your airbag may not deploy in a collision, or that your seatbelts may fail to tighten when braking, posing a significant risk.
ESC (Electronic Stability Control) and traction control light – This indicates a malfunction that could cause the vehicle to lose control and skid. If the light remains illuminated for more than a few seconds, it will lead to an automatic MOT failure.

How can Formula One Autocentres help?

Here at Formula One Autocentres, our qualified engineers can inspect all external lights and dashboard warning lights before your MOT test and replace any faulty bulbs. Replacement bulbs are stocked across our branches, and fitting is fast and straightforward. If there is an underlying fault, we can also carry out diagnostic checks to pinpoint the issue. Book your MOT and service together to save; an MOT booked together with a service starts from £29.50. Use our branch finder to book an MOT, service or diagnostic appointment.