How to Check Your Dashboard Warning Lights Before an MOT
A UK checklist for dashboard warning lights before an MOT: which lamps fail the test, how to read the fault behind them and what to fix first.
To check your dashboard warning lights before an MOT, turn the ignition to position two without starting, watch which lamps light up and then go out, and note any that stay on. A lamp still lit for the engine, airbag, ABS, ESC, brakes, power steering or TPMS points to a fault the tester will fail — so investigate it first.
Why warning lamps matter on test day
The MOT is not just a check of brakes and tyres; it also checks that key warning lamps work and are not signalling a fault. GOV.UK’s list of parts checked at an MOT confirms testers look at the malfunction indicator lamps for airbags, seatbelt pretensioners, ABS, ESC, the electronic parking brake and brake fluid, plus power steering and — on cars first used from 1 January 2012 — the tyre pressure monitoring system. The engine management light (MIL) is checked separately under the emissions rules.
The logic is simple: these lamps do a bulb-check when you switch on, then go out. If one stays on, the system it represents is reporting a problem, and a reported fault on a safety or emissions system is a failure.
The pre-MOT lamp walk-through
Do this with the car cold, on a level surface:
- Ignition on, engine off. Turn the key to position two (or press start without your foot on the brake in a keyless car). The cluster should illuminate a row of lamps.
- Watch them extinguish. Most should go out within a few seconds; some, like the diesel glow-plug lamp, go out as the engine is ready to start.
- Note the stragglers. Any lamp still on after start-up is your priority list — especially engine, airbag/SRS, ABS, ESC, brake, power steering and TPMS.
- Check the bulbs work at all. A lamp that never lights can be a problem too: the tester needs to see it function. The engine MIL specifically must illuminate and then go out.
If everything lights and clears correctly, you have passed the visual half of the job. If not, you need to know what is behind the lamp.
Turning a lamp into a diagnosis
A warning lamp tells you a system is unhappy, not why. This is where a scanner earns its place. Plugging in a full-system tool such as the TOPDON CarPal lets you read the stored fault code behind the lamp on supported vehicles, so an amber airbag light becomes, say, a specific seat-occupancy sensor code rather than a mystery.
Read the codes, note them and their status, and save any freeze-frame data before clearing anything. Clearing the code without repairing the cause simply hides the lamp temporarily; on a safety system it will return, and it may reappear before or during the test. For a system-by-system breakdown of what does and does not fail, see our guide to which dashboard warning lights fail an MOT.
Which lit lamps are most likely to fail you
- Engine management light (MIL): an illuminated MIL indicating a malfunction is a major fault under the emissions rules.
- Airbag/SRS: fails only when the lamp indicates a system malfunction; a passenger-airbag-disabled lamp is not itself a defect.
- ABS and ESC: fail when the lamp indicates a malfunction of that system.
- Brake fluid and electronic parking brake: checked and can fail when indicating a fault.
- Power steering: a malfunction indication is a fail.
- TPMS: on 2012-onward cars, a TPMS lamp indicating a fault is a fail — and note it can stay on if a sensor is genuinely faulty, not just because a tyre is soft.
Build it into a repeatable routine
Learning how to check dashboard warning lights before an MOT is worth turning into a habit you run a week or two before every test, not a panic on the morning. A week’s notice gives you time to order a bulb, book a garage slot for a genuine ABS or airbag fault, or complete a drive cycle after a repair. Keep it simple: ignition on, watch the lamps light and clear, note any that stay on, and read the code behind anything that does. Do the same walk-round for the lamps that share the safety story — brake fluid, power steering, ESC and TPMS — because these are all checked and all capable of failing you. If your car has a head-up display or a digital cluster, remember warning messages on the screen are not defects in their own right, but they can confirm that a lamp is on because a real fault exists. Writing down what you find, and what you did about it, means next year’s check starts from a known baseline rather than a blank sheet.
Fix the cause, then verify
Once you know the code, deal with the root cause rather than the symptom. After the repair, clear the code, then drive a normal mix of roads so any emissions monitors can complete, and re-scan to confirm the lamp stays off and no pending code is lurking. That final re-scan is the difference between hoping and knowing.
Frequently asked questions
Will an amber engine light fail an MOT?
If the engine management light is illuminated to indicate a malfunction, it is a major fault and a failure. A lamp that completes its bulb-check and goes out is fine.
Is a passenger airbag “off” light a failure?
No. A lamp showing the passenger airbag has been deliberately deactivated is not treated as a defect. Only an SRS lamp indicating a system malfunction fails.
Can I just clear the lights before the test?
Clearing a code without fixing the fault is a false economy. On safety and emissions systems the lamp returns once the car re-runs its checks, and the tester will see it. Diagnose and repair first.