Dashboard Warning Lights Before MOT: What Drivers Should Know

Which warning lights matter for the MOT

Since the 2018 MOT rules tightened, several dashboard warning lights are an automatic fail — even if the car otherwise drives perfectly. The tester doesn't need to prove the underlying fault; the illuminated lamp is the defect.

• Engine management (EML / check-engine)
• ABS
• Airbag / SRS
• Electronic stability control (ESC / ESP)
• Brake system warning
• Power steering (EPAS) on most cars after 2012
• Tyre pressure monitoring (TPMS) on most cars after 2012
• Emissions / particulate filter (DPF) warning on diesels

Solid vs flashing lights

A solid amber light usually means 'investigate soon'. A flashing light — especially the engine-management lamp — means stop driving and call a garage. Flashing EML on a petrol car typically signals misfire that can wreck the catalytic converter within minutes.

What to do before booking the MOT

• Note which lights are on, when they came on and whether the car behaves differently
• Check the dipped headlights, indicators and brake lights work — bulb failures often trigger a CAN bus warning
• Top up screenwash, brake fluid and coolant to the MAX line — low-level warnings will cause a test fail
• If the EML is on, get a diagnostic scan before the test rather than after a fail — it's cheaper and faster

When to call a garage

Any red warning light, any flashing light, any combination of ABS + brake light, or a warning that returns after you reset it — book a diagnostic. We charge £45 for a full scan and the fee comes off any repair work we do.

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