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Most common causes of MOT failure

We look at the five most common reasons that cars fail their MOT, and show you what you can do to help your car pass first time.

Tyres are a common cause of MOT failure

Tyres are a common cause of MOT failure

According to the Driver and Vehicle Standards Agency (DVSA), 40% of vehicles fail their MOT at the first attempt. However, the good news is that nearly half of the most common faults can be fixed with some simple regular maintenance.

From bulbs and bumper stickers to tyres and top-ups, we find out the main causes of failure and suggest easy ways to help you ace your MOT.

Headlamps and lightbulbs

30% of MOT failures are to do with lightbulbs, headlight angles and signalling. While you might need a mechanic to quickly read just your headlamp positioning, you can easily replace spent lightbulbs yourself, and it’s sensible to have a supply of spares, especially in the winter months when the clocks go back.

So be a bright spark, and don’t let something as tiny as a registration plate bulb replacement (which is responsible for 17% of MOT fails) be your downfall.

Tyre condition and pressure

Checking your tyres is a vital part of staying safe on the road, yet over 10% of cars failed their MOT last year because of insufficient tread or pressure. If your tyre tread is less than 1.6mm, then you must replace them immediately.

A quick way to check your tyre tread depth is to do the 20p test. Just insert a 20p coin into the main grooves of your tyre–if you can’t see the outer band of the coin, your tread depth is fine, if you can, it’s time to replace.

Similarly, you need to check your tyre pressure regularly. Not only does a quick trip to the petrol station to inflate your tyres save you money on running costs, it could be the difference between an MOT pass or a fail.

Watch our video to find out more about checking your tyres.


Driver’s view of the road

Are your windscreen wipers past their best? If you’ve got a smeared screen, it’s not expensive to replace your wipers, and much easier than getting a black mark at your MOT.

Anything that obscures a driver’s view of the road is a big no-no, with 8% of cars failing their MOT due to worn wipers, cracked mirrors or even a lack of screenwash – so don’t forget to top that up before you go.


It’s also a good idea to remove any stickers from your windscreen or back window. Do you really need that enormous bumper sticker from a trip to Edinburgh Zoo five years ago? Probably not.


One in ten cars fail their MOT due to brake problems. If you think there’s something wrong with your brakes – for example, if your car starts pulling to one side, always ask a mechanic to take a look.

However, you can maintain your brakes by checking them every day as you set off. Also, stay aware of your brake fluid levels by looking out for the high/low markings on the reservoir – usually it’ll need to be topped up every two years. Finally, before you take your car for its MOT, ask a friend to ensure your brake lights are coming on, and change the bulbs if there’s a problem. (See number 1)

Number plates and cleanliness

Did you know that your garage can refuse to give you an MOT if you have an excessively cluttered or grimy car? If yours looks like a landfill, give it a good clean before you go in, and always make sure your number plate is legible, i.e. not covered in a layer of mud! Avoidable number plate issues account for 4% of MOT fails, so also check it’s secured to the car properly.

Top tip: Top up your oil, too!

Fuel and engine oil needs to be topped up before you put your car in for its MOT, otherwise you’ll be turned away. This is because your mechanic will need to test your car’s emissions. So, follow these tips and hopefully your car will pass with flying colours.


About the Author

Lucy Sweet

Staff writer at Arnold Clark