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WHAT THE GUIDANCE SAYS
Your car runs its own diagnostics.
Modern cars check their engines, brakes, airbags and tyres and report problems with a warning lamp. The Highway Code says to understand those lights, and several of them can fail an MOT.
Check a light Read the short answer
THE SHORT ANSWER
Warning lamps should go out once the engine starts.
If one stays on, or comes on while driving, check it.
THE HIGHWAY CODE
Warning lights come on with the ignition and should go out when the engine starts, except the handbrake light. If they stay on or come on while driving, the Highway Code says to stop and investigate.
Check a lightAT THE MOT
The DVSA manual lists an engine MIL indicating a malfunction as a major defect, alongside ABS, airbag (SRS), stability control and power steering warning lamps showing a fault.
See the datesTYRES
For cars first used from 1 January 2012, a tyre pressure monitoring system that is malfunctioning or obviously not working is a major MOT defect.
What to doA QUICK DASHBOARD CHECK
Pick a warning lamp to see how the DVSA MOT inspection manual for cars treats it. The bar shows how serious the MOT defect category is.
Based on the DVSA MOT inspection manual for cars and passenger vehicles (GOV.UK). This is general information, not legal or mechanical advice: check your handbook or a garage.
TWO NUMBERS WORTH KNOWING
One date for the engine light,
one for the tyre pressure warning.
ENGINE MIL · DVSA
Petrol cars checked if first used from
2003<small> onwards</small>
Testers inspect the engine MIL on petrol cars, including hybrids, first used on or after 1 July 2003, and on diesel vehicles first used on or after 1 July 2008.
TYRE PRESSURE · DVSA
Cars checked if first used from
2012<small> onwards</small>
The tyre pressure monitoring system is inspected on passenger cars first used on or after 1 January 2012. A system that is malfunctioning or obviously not working is a major defect.
Since 20 May 2018 MOT defects in England, Scotland and Wales are graded dangerous, major or minor. Dangerous and major defects are fails; minor defects and advisories still pass.
FOUR HABITS FOR DRIVERS
Warning lamps are easiest to deal with when you notice them early. These habits come from the Highway Code and the MOT manual.
HOW MOT RESULTS WORK
The DVSA grades every defect. A dangerous defect is a direct and immediate risk to road safety: do not drive until it is repaired. A major defect may affect safety or the environment and should be repaired immediately. Both mean a fail.
A minor defect has no significant effect on safety and should be repaired as soon as possible; an advisory could become more serious and should be monitored. Dashboard messages are not defects on their own, but help a tester confirm a lamp is showing a fault.
QUESTIONS PEOPLE ASK
Yes, if it applies to your vehicle. The DVSA manual lists an engine MIL that is inoperative or indicating a malfunction as a major defect for petrol cars first used from 1 July 2003 and diesels first used from 1 July 2008.
The manual lists warning lamps showing a malfunction for the engine, ABS, airbags (SRS), electronic stability control, electric power steering, electronic parking brake and tyre pressure monitoring (cars from 2012) as major defects.
Yes. The Highway Code says warning lights light up when you turn the ignition and go out when the engine starts, except the handbrake warning light. If they stay on, stop and investigate.
No. The manual says a lamp lit to show that the passenger airbag is disabled is not a defect. Only an SRS lamp indicating a system malfunction fails.
Not on its own. The DVSA manual says dashboard warning messages are not a defect in their own right, but they can help the tester confirm that a warning lamp is lit because a malfunction exists.
SOURCES
Each figure on this page comes from the sources below. Check them for the full detail and context.
