The 10 most common MOT fails and how to avoid them

Your annual MOT can instill fear into even the most confident and assured of drivers - because no matter how good you are, there’s no guarantee your car is in equally good shape.

In fact, official statistics for 2015/16 show over 36% of cars failed their MOT at the first time of asking – equivalent to almost 7.8 million tests – and the average fail was the result of almost 3 defects. Many of the defects causing the failures are easy to remedy, and could have easily been resolved before the test.

We’ve put together this quick guide outlining the most common failures – and how you can prevent them.

Lights and signaling

Blown bulbs are the single biggest cause of failures, and are one of the simplest and cheapest to fix. Before the test, enroll a friend to help you check all of the lights are working – front, rear, indicators (including side repeaters), brake lights (including central repeaters), and fog lights front and back.

You can also fail if the headlights have deflectors fitted for driving in Europe, and you’ve forgotten to remove them. Make sure they’ve come off after you get home.


Britain’s potholed, patchworked road surfaces give our car’s suspension a severe workout, and suspension failures are increasingly common – featuring in over 1 in 10 tests. Short of clambering beneath the car there’s little you can do pre-test, to prevent a failure; instead time your annual service for just before the test and an expert can let you know.


Keep an eye out for spongey pedal feel and the car pulling to the left or right under braking – it’s a sign that the pads might need replacing. On average, brakes should need refreshing at about 50,000 miles, but it may be sooner or later depending on your driving style.


Your tyres are the only part of the car physically in contact with the road – so they should be regularly checked throughout the year to ensure they’re in good condition. Use a 20p piece to check the tread depth across the full width of the tyre, and all the way around. If the outer band of the coin is visible, your tyres could be under the legal limit.

Driver’s view of the road

Being able to see all around is important, so your car could fail if the windscreen has a crack, or even if you simply leave a windscreen-mounted phone cradle in position for the test. Your windscreen washers must also work, so fill the reservoir and test that the pump is still working as normal.

Remove any cradles or stickers, and get windscreen chips filled with resin before it becomes a crack. You should also ensure that at least one rear view mirror is intact and adjustable; replacement, stick-on mirror surfaces can be found at little cost.

Fuel and exhaust

Emissions – especially on diesel vehicles – are an increasing cause of failures. It’s become so common that ‘Pre-MOT’ fuel treatment packs are now on sale, helping to clean out the fuel system before the test. It’s also a good idea to give the car a long pre-test run at high revs (like on a motorway), to warm the engine up and blow out any cobwebs.


Fluids are not generally checked during an MOT test, but one that is tested is power steering fluid – the amount in the reservoir must be at least at the minimum level. Give it a check in advance and get it topped up if necessary.

Seat belts and airbags

Seat belts must retract, so take a few minutes to resolve any twisted or knotted belts and make sure that they all secure in position, without detaching. A missing airbag (or an airbag warning light on your dashboard) will also cause a failure – warning lights that have come on in error can often be reset at a garage for a small fee.

Body and structure

There’s not much you can do about rust (other than washing the car regularly during winter, when corrosive grit/salt can settle in wheel arches) - but any loose, sharp edges will cause a fail. So repair any accident damage, such as loose bumpers, in a timely fashion.

Registration plates

Your plates must be visible and legible, so your car could fail simply because it’s filthy or the light illuminating it at night has blown! Check this while checking your other lights, and give the plates a quick wipe with a wet cloth.