Each year in the UK, nearly one in five vehicles fails its MOT test, with roughly 22.6 percent of tests resulting in failure during 2023 alone. Most failures stem from issues that are fully preventable with a few simple checks and maintenance. This guide covers the most common causes, what causes them and how you can fix them early to help you pass your MOT confidently and avoid repeat fees.
Faulty Lighting & Electrical Equipment
The most frequent cause of MOT failure involves lamps, reflectors and electrical components. Broken or misaligned headlights, faulty indicators, brake lights or registration plate bulbs can all lead to major or dangerous faults.
To avoid this, walk around your car before your MOT with someone activating each light. Replace any blown bulbs, clean the lenses, ensure indicators and brake lights work correctly, and check the horn, mirrors and dashboard warning lights, as all are common failure points.
Suspension Wear
Suspension-related failures account for a significant number of MOT rejections. Items like worn shock absorbers, failing springs or bushings can affect handling and safety, especially at higher speeds or over bumps.
You can help prevent this by listening for knock or clunk noises during turns or braking, checking ride height, and looking for leaks or visible damage to dampers. If your car handles poorly, a suspension check at a service centre may be needed.
Tyre & Wheel Issues
Tyres and wheels make up a considerable portion of MOT failures. A tyre measured below the legal tread depth of 1.6 mm, or tyres with bulges, cuts or uneven wear, often fails with a dangerous defect flag.
Checking your tread depth with a 20p coin, assessing pressure, checking for even wear and inspecting sidewall condition can all help. Replace any tyres below the legal limit before the test and consider rotating them if the wear is uneven.
Brake Related Faults
Brakes are the third most common reason for failure. Faults can range from worn brake pads and low fluid levels to ineffective braking performance flagged during testing.
To reduce the risk, listen for squeals or grinding, ensure the brake pedal feels firm and confirm the brakes respond evenly when applied. If you notice any warnings, a diagnostic scan can help check brake fluid condition, ECU inputs and other issues before the MOT.
Windscreen, Wipers & Visibility
Problems affecting visibility such as windscreen chips, cracked mirrors, poorly aligned number plates or ineffective wipers are frequent triggers for MOT failure.
You should repair any significant windscreen damage, replace worn wiper blades, top up washer fluid and clean or replace number plates as needed before your test.
Emissions & Exhaust Defects
Smoke emissions, rattling exhausts or lambda sensor failures can lead to an MOT fail, especially for diesel vehicles. Current standards require clean performance.
Check for visible smoke, listen for unusual exhaust noises and ensure warning lights are not illuminated. A diagnostic scan can also identify lambda sensor or ECU errors contributing to emission problems.
Body Structure & Other Safety Issues
Although less common, issues like rusted mountings, faulty door closures, missing mirrors or broken hinges can lead to failure under the body structure or attachments category.
Inspect the vehicle’s bodywork for sharp edges or protrusions. Ensure that doors open and close correctly, that seat belts retract and lock properly and that no structural panel is excessively corroded.
Preventable Faults & DIY Fixes
It is striking how many MOT failures result from simple neglect. DVSA reports show over 2.5 million failures in 2024 came from basic issues like burnt out bulbs, worn tyres or low fluids, all of which can be fixed at home.
Small investments in maintenance such as regular tyre checks, bulb replacements and fluid top ups can save you repeat test fees and unnecessary garage visits.
Book A Pre MOT Check With Confidence
Preventable failures such as worn tyres, electrical faults or brake issues make up the majority of MOT test failures. If you are unsure whether your vehicle is ready, booking a pre MOT inspection can save stress, money and ensure compliance with emission testing standards and MOT inspector expectations.
Contact your local garage today to arrange a diagnostic scan or MOT pre check. Our trained technicians will help address issues before they become major faults, keeping you safe, legal and roadworthy.