MOT Failures Explained: The Most Common Reasons Cars Fail
An MOT test is a legal requirement for most vehicles over three years old in the UK. Yet every year, millions of cars fail their MOT - often for reasons that could have been easily fixed in advance. Whether you’re buying a used car or trying to keep your current vehicle road‑legal, understanding the most common MOT failure points can save you time, money, and stress. Below, we break down the most common reasons cars fail an MOT, what they mean, and how you can avoid them.
1. Lighting and Signalling Issues
Faulty lights are the single most common MOT failure reason. Even something as minor as a blown bulb can cause a fail.
Common lighting failures include:
- Headlights not working or incorrectly aligned Brake lights or indicators not functioning
- Fog lights staying on or not working
- Number plate lights not illuminating properly
How to avoid it: Do a full light check regularly, especially before your MOT. Ask someone to help you check brake lights and indicators, or park near a reflective surface.
2. Tyres and Wheels
Tyres are a major safety component and are closely inspected during an MOT.
Typical tyre-related failures:
- Tread depth below the legal minimum of 1.6mm
- Uneven or excessive tyre wear
- Visible damage such as cuts, bulges, or exposed cords Incorrect tyre size or mismatched tyres on the same axle
How to avoid it: Check tyre tread depth monthly and inspect tyres for damage. Replace worn tyres early rather than risking a fail - or worse, a blowout.
3. Braking System Problems
Brake issues are taken very seriously during an MOT due to safety risks.
Common brake failures include:
- Worn brake pads or discs Poor brake performance or imbalance
- Faulty handbrake or excessive travel
- Warning lights illuminated on the dashboard
How to avoid it: Listen for squealing or grinding noises and address brake warning lights immediately. Regular servicing helps catch issues early.
4. Suspension and Steering Faults
Suspension and steering components affect handling, stability, and tyre wear.
Frequent failures include:
- Worn shock absorbers
- Damaged springs
- Excessive play in steering components
- Leaking suspension parts
How to avoid it: If your car feels unstable, pulls to one side, or makes knocking noises over bumps, get it checked before your MOT.
5. Exhaust and Emissions Failures
Emissions testing is a common stumbling block, particularly for older vehicles.
Reasons cars fail emissions tests:
- Faulty catalytic converter
- Exhaust leaks
- Engine management warning light on
- Poor fuel combustion due to engine faults
How to avoid it: Make sure your car is properly serviced and consider a longer drive before the test to warm up the engine and catalytic converter. AT David Hayton, we offer full servicing options to ensure you’re never without your vehicle.
6. Windscreen, Wipers, and Washer Issues
Visibility is essential for safe driving and strictly assessed.
Common failures include:
- Cracks or chips in the driver’s line of sight
- Worn or damaged wiper blades
- Washer system not working or low fluid
How to avoid it: Top up washer fluid regularly and replace worn wipers annually. Repair windscreen chips before they spread.
7. Seatbelts and Safety Features
Seatbelts must be fully functional and securely fitted.
Failure reasons include:
- Seatbelts not retracting properly
- Frayed or damaged belts
- Warning lights staying illuminated
How to avoid it: Check that all seatbelts pull out smoothly and lock under tension. Never ignore airbag or seatbelt warning lights.
8. Dashboard Warning Lights
Modern vehicles rely heavily on electronic systems, and warning lights are closely monitored.
Instant MOT failure lights include:
- Engine management light
- ABS warning light
- Airbag (SRS) warning light
How to avoid it: If a warning light appears, get a diagnostic check well before your MOT appointment.
Buying a Used Car? Check MOT History
If you’re purchasing a used car, always review its MOT history. Repeated failures for the same issues could indicate poor maintenance or underlying problems. A clean MOT history doesn’t guarantee a perfect car - but it’s a strong indicator of responsible ownership.
Many MOT failures can be avoided with a few simple checks and regular vehicle maintenance. Knowing the most common reasons cars fail their MOT can make a big difference, helping you pass first time while keeping your vehicle safe, reliable and fully road legal. Whether you’re getting ready for your next MOT or considering the purchase of a used car, a little expert insight goes a long way, and at David Hayton Autostore, we believe it could save you hundreds of pounds in unnecessary repair costs. Book in your next service & MOT today, and let us take care of your vehicle.
