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Common causes of MoT failure….and what you can do to fix them!

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Diagnostics & Test Equipment Maintenance Solutions Technical Tip 4 min read

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In this article, you will find out about the common causes of MoT failure and what you can do to fix them. 

Did you know that nearly half of all faults found on MoTs are surprisingly easy and cheap to fix? Here we give you an insight into the most common failures and what you can do to prevent them – either by yourself, with some simple maintenance, or with the help of a qualified technician.

Lighting and signaling.

Nearly one in five of all cars fail their MoT because of a problem with their lights and/or indicators. Annoyingly, this could be something as simple as a blown bulb. Whilst most modern cars will display a warning light if a bulb is out, it’s worth checking the condition of your lights every so often for faults, damage or dirt. Not only will it help get you through your next test, it will avoid the risk of a fine, and critically keep you and others safe. Simply switch on your lights, check each of them is working, and give them a gentle tap to identify any loose or damaged components. Lights to check include; indicators, reversing lights, brake lights, fog lights and even your registration plate bulb. Replacement bulbs are relatively cheap and quick to fit. Note under new MoT standards which come into force on 20th May, faulty reverse lights will now result in a failure.


With the deterioration of UK roads, it should come as no surprise that ride and handling issues are one of the fastest growing fail points. In fact, it’s the cause of more than one in 10 failures. Unfortunately, whilst a worn suspension component isn’t as obvious, there are some common signs to watch for. If your car is riding roughly i.e. you can feel every bump in the road, making unusual clunking sounds, drifting or pulling during turns, nose diving at stops or sitting low in one corner then you may have a suspension issue. Another good indicator is the bounce test; with the handbrake on, press down on one corner with all your weight – if the car rocks or bounces a few times after you’ve released it, then it’s likely the suspension is wearing out. Since poor suspension can affect the stability and control of your vehicle, it’s important to get any issues checked out by a qualified technician as soon as possible.


Worryingly one in 10 cars fail their MoT due to this safety critical system, and all too often there are obvious warning signs. Squealing or grinding sounds, a soft brake pedal, vibrations in the steering wheel and/or pedals and the car pulling to one side when braking are all indications that something isn’t working as it should. Visual clues are equally important; inspect your pads and discs for signs of wear and tear and your brake fluid levels – if it’s below the minimum level, top it up with the correct specification fluid, and have the brake system checked by a trained technician.  You should also check your handbrake. Simply stop on a hill and apply the handbrake – you shouldn’t have to push or pull too hard to do this, and critically, it should hold the car. If you suspect you have an issue with your brakes, have your car inspected by an experienced technician straight away.


Checking your tyres regularly is an absolute must, yet over 10 percent of cars fail their MoT because of insufficient tread, pressure and/or poor tyre condition. A quick way to check your tread depth is to do the 20p test as its outer band is the same as the minimum legal tread depth, 1.6mm; simply insert the coin into the tread, and if you can still see some of the band, then you’ll need a new tyre. Similarly, check your tyre pressure, including the spare, is in line with the specifications detailed in your owner’s manual. It could save you money on fuel as well. And finally inspect each tyre for any signs of damage including cracked rubber, cuts or bulges on both the inner and outer sidewalls. If you spot any issues, have your tyres checked immediately at a reputable garage or tyre fitter.

View of the road.

It stands to reason that you’ll want a clear view of the road, yet alarmingly around 7 percent of MoT fails are due to issues with the driver’s visibility. This includes worn windscreen wipers, cracks or chips, rear view mirrors and even items that may obscure your eyeline such as sat navs and air fresheners. Some of these are an easy fix. If your wipers are cracked or split, replace them – it’s a quick and relatively cheap job. Check your screenwash levels, topping up the bottle if needed. Last but not least, make sure your screen is clean and remove any distracting objects. You should also get your windscreen replaced if you have any large chips that affect your view.

Did you know that from 20th May 2018, changes to the testing procedures and standards for MoTs in England, Scotland and Wales come into effect? These include new defect categories and tougher rules for diesel cars. But just remember, by following the above advice, you’ll be well on your way to passing your next test with flying colours.

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