Warning Lights That Cause an MOT Failure

Which Warning Lights Cause an MOT Failure?

Some dashboard warning lights will fail an MOT and some will not. The ones that fail are those showing that a safety or emissions system has a fault, such as the engine management, ABS, airbag and brake warning lights. Lights that are not about a safety system, like low fuel, have no effect on the test.

The rule is really about what the light is telling you. A warning light that stays on to show a system is not working correctly points to a genuine fault, so the MOT treats it as a failure. A simple reminder or an information light does not carry the same weight. Our overview on What Is an MOT explains where these checks sit in the wider test.

A common surprise is the engine management light. Since 2018 an illuminated engine management light that shows a fault has been a failure, so it can no longer be ignored in the hope the car slips through. It is far better to have the cause looked at before the test.

Warning Lights That Fail an MOT

A handful of specific warning lights will fail the test if they are showing a fault. The table below lists the main ones and what they relate to.

Each of these points to a safety or emissions system that is not working as it should. The brake and ABS lights tie directly into how the car stops, which our guide on Brakes and the MOT covers in detail.

Warning Lights That Do Not Fail

Not every light on the dashboard matters for the MOT. Plenty of lights are there to inform rather than to warn of a safety fault, so these do not affect the test result.

A low fuel light, a low washer fluid warning, a service due reminder or a general information light will not cause a failure. The test is concerned with the safety and emissions systems, not with routine reminders. That said, a service reminder is still worth acting on, since keeping the car serviced helps it pass everything else. Our guide on Top Reasons Cars Fail MOT covers the faults that most often cause a fail.

What to Do About a Warning Light

If a warning light is showing before your MOT, the sensible step is to find out why rather than hoping it clears. Some lights come on briefly and go out as the car starts, which is normal. A light that stays on is telling you a system needs attention.

Having the fault read and fixed before the test avoids a wasted fail and, more importantly, deals with a genuine issue on the car. Many of these warnings relate to safety systems you rely on every day, so they are worth sorting for their own sake. Booking with a garage that can diagnose and repair in one visit makes this simple.

Why the Engine Light Now Matters More

The engine management light deserves its own mention, because the rules around it tightened in 2018. Before then a glowing engine light did not automatically fail a car. Since the rules changed, an illuminated engine management light that shows a genuine fault is a failure, so it can no longer be cleared and ignored in the hope the car passes.

This matters because the engine light often points to an emissions related fault, which the test takes seriously. Clearing the code without fixing the cause rarely works, as the light usually returns once the car is driven. The reliable approach is to have the fault read properly and put right, which also stops the car wasting fuel. Our guide on Emissions and the MOT explains the emissions checks the light can relate to.

Clear the Warnings

This guide is part of our full MOT Guides hub, where the testing, cost and rules articles sit together so you can move to the exact detail you need next. When it is time to book, our team offers full MOT testing and repairs from our centre in Ely. You may also find it useful to read What an MOT Checks, Brakes and the MOT and Top Reasons Cars Fail MOT.

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