MOT failure: what fails an MOT?​

Driver and Vehicle Standards Agency (DVSA) statistics from July to September 2019 show that 31.4% of all vehicles experienced an initial MOT failure, with 31.7% of all Class 3 and 4 vehicles (cars, vans, and passenger vehicles up to 12 seats) failing their MOTs.
While we all want our MOTs to pass with flying colours, MOTs are in-depth tests and there are plenty of things that will fail an MOT. Driving without an MOT is illegal – in this guide, we look at the background behind what can fail an MOT, common MOT failure reasons, and what to do if your vehicle fails its MOT and you need a service or retest.

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So, what are the reasons for MOT failure? Changes made to the MOT test criteria back in 2018 mean that rather than individual elements being marked as a pass or fail, defects are now classified as dangerous, major, minor, or advisories. MOT failure depends on this classification.

  • Dangerous defects – A car with a dangerous defect will fail its MOT and cannot be driven in any circumstances – even to an MOT test centre or workshop for repairs. The law requires that the defect must be repaired before the car is driven.

  • Major defects – Major defects cause MOT failure, but the vehicle can be driven with a major defect if it still has time left on the old MOT certificate. If it has expired, the car can only be driven to a workshop at the time of an appointment, and you must have record of the appointment that can be shown to the police if you are pulled over.

  • Minor defects – A minor defect is not a cause of MOT failure. They are defective components, but not ones that are serious enough to require an immediate repair and retest. The government advises these are repaired as soon as possible.

  • Advisories – An advisory is used for parts that are not broken but will likely soon require repair either as a minor, major, or dangerous defect.

The specific MOT failure reasons and their classifications will be shown to you on the VT30 form provided by the MOT test centre. Visit the government’s website to see an example.

Common MOT failures

Certain parts of vehicles experience MOT failure more commonly than others, due to the way cars are designed, being more likely to experience wear, and so forth. But exactly what will fail an MOT?

Below, we take a look at the most common MOT fail defects based on DVA data for cars and vans from Q2 2019, as well as common customer queries regarding which parts constitute a failure.

  • Lamps, reflectors, and electrical equipment – The most common MOT failure class, accounting for 27% of all defects, included lamps, reflectors, and electrical equipment. It’s easy to see why, since cars are now so dependent on electrical systems, said systems are complex and much more liable to fault than other more mechanical vehicle components.

  • Suspension – Vehicle suspension systems made up 18.1% of all MOT failure defects. With potholes and other uneven surfaces commonly encountered throughout the UK road network, suspension systems certainly take the brunt of bumps and shocks.

  • Brakes – Braking systems comprised 16.8% of all defects that caused an MOT failure. We use our brakes constantly in the UK, particularly in stop-start urban driving.

  • Tyres – Constantly in contact with the road and affected by the changeable and often extreme British weather, tyres caused 11.6% of failure defects in Q2 2019.

  • Visibility – 8% of MOT failure defects were related to the visibility section of the MOT test. This includes the field of vision, glass condition, rear view, wipers and washers.


Are worn brake discs an MOT failure reason?

Yes, a brake disc which is worn below its minimum thickness will be classed as a major fault, resulting in an MOT failure. A loose brake disc will be classified as a dangerous defect, which means the car cannot be driven until the defect is repaired.
A brake disc which is worn close to its minimum will result in an advisory note but will not constitute an MOT failure.

Is a windscreen crack an MOT failure?

Yes, a windscreen crack in front of the driver more than 10mm in diameter, or in the rest of the windscreen more than 40mm in diameter, will constitute a major or dangerous failure, depending on how extreme the crack is. If the crack is smaller than this, then it will be classed as a minor fault.
Scratching, discolouration, and excessive tinting can also be classified as a dangerous, major, or minor defect.

Will my car fail its MOT if my spare tyre is bald?

If your spare tyre is not currently fitted to your axle, it will not be inspected as part of an MOT. If it is fitted, you may fail your MOT as all tyres fitted must be compatible with all three other tyres and be in good condition, or other issues may have arisen from the puncture event, such as wheel or suspension damage.
That said, if your spare tyre is not road legal, it is of no use if you have a puncture. If this is the case with your spare, pop into your local Protyre garage and look at our range of tyres, including premium brands such as Pirelli, Bridgestone, and Falken.

Will my car fail its MOT test if the front fog lights are broken?

DVSA guidance notes that front fog lamps are inspected during your MOT test if your car was first used on or after 1st March 2018. Rear fog lamps are checked if your vehicle was first driven on or after 1st April 1980. If your vehicle isn't fitted with front and rear position lamps, then a rear fog lamp is not required. If these rules apply to your vehicle, it is essential to check your fog lights are working before bringing in your vehicle for testing.

Is a broken number plate light an MOT failure?

Yes, broken front or rear number plate lights constitute a major MOT failure. That’s because they are crucial in allowing other vehicles and the police to identify a vehicle at night or in bad weather. Coloured number plate lights are also illegal and will cause your car to fail its MOT.

Can an oil leak fail my MOT?

If your car is leaking oil or any other fluid, and it creates a 75mm diameter pool on the floor within five minutes, then it will be given a major MOT fail mark if it is likely to harm the environment or pose a general safety risk. It’ll get a dangerous mark if it is a serious risk to road safety.

What to do next if you fail your MOT

If your car fails its MOT, you need to book a retest. Find out how in our simple and straightforward guide to MOT failures and retests below.

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Book your test below, or get in touch if you have any questions – online or over the phone.

At Protyre Autocare, we provide thorough MOT testing to ensure your vehicle meets all safety and environmental standards. During your MOT, it's crucial to have tyres that are in good condition. Explore our range of tyre types, including premium car tyres, rft tyres, best summer tyres, and winter snow tyres. We also offer a variety of trusted premium tyre brands such as Goodyear all season tyres, Michelin tyre, Pirelli tyres, Bridgestone turanza, Conti tyres, and many more. Ensuring you have the right tyres can make a significant difference in passing your MOT and maintaining your vehicle’s safety and performance.