Quick answer
Warning lights, tyre damage, brake noise, heavy smoke, suspension knocking or serious rust should be checked before the MOT test.
The most common MOT failure reasons in the UK are worn tyres, faulty lights, brake problems, suspension wear, rust, emissions faults, warning lights, steering problems and visibility issues.
Many MOT failures can be avoided by checking the car properly before the test. Look for worn tyres, warning lights, faulty bulbs, damaged wipers, brake noise, knocking suspension, fluid leaks, heavy exhaust smoke and visible corrosion.
Detailed MOT failure guides
This page is the main common MOT failure guide. For more detailed advice, use the individual guides below. These pages connect the main MOT topic to your specialist brake, tyre, rust, suspension, emissions and lighting guides.
Brake MOT failures
Worn brake pads, brake imbalance, weak braking force, brake warning lights, handbrake problems and brake fluid leaks explained.
Read brake MOT failure guide →Tyre MOT failures
Low tread, tyre bulges, sidewall damage, exposed cords, uneven tyre wear and tyre pressure warning light issues explained.
Read tyre MOT failure guide →Rust MOT failures
Structural corrosion, sill rust, chassis rust and corrosion near suspension, steering or seatbelt mounting points explained.
Read rust MOT failure guide →Suspension MOT failures
Broken springs, worn bushes, leaking shock absorbers, ball joints, anti-roll bar links and knocking suspension explained.
Read suspension MOT failure guide →Emissions MOT failures
Exhaust smoke, DPF problems, catalytic converter faults, exhaust leaks, lambda sensor issues and engine warning lights explained.
Read emissions MOT failure guide →Lights MOT failures
Headlights, brake lights, indicators, fog lights, side lights, tail lights, cracked lenses and number plate lights explained.
Read lights MOT failure guide →MOT legal rules after failure or expiry
Failing an MOT is not just a repair issue. It can affect whether you can drive, whether the car can stay on the road, how police checks work, insurance claims, vehicle tax and SORN decisions.
What happens if your car fails MOT?
Understand major defects, dangerous defects, MOT retests, repair choices and what to do after the failure sheet is issued.
Read failed MOT guide →Can you drive a car with failed MOT?
Learn when driving after MOT failure may be allowed and when the car should not be driven at all.
Read driving after failed MOT guide →Driving with expired MOT fine UK
Understand fines, police checks, insurance concerns and legal exceptions for expired MOT vehicles.
Read expired MOT fine guide →Can police see no MOT?
Police and ANPR systems can check MOT status electronically using vehicle registration details.
Read police MOT check guide →Can you park a car on the road without MOT?
Find out whether a no-MOT vehicle can be left on a public road and what to do if the MOT has expired.
Read parking without MOT guide →Does SORN car need insurance?
Learn how SORN affects insurance, road use, off-road storage and returning a vehicle to the road.
Read SORN insurance guide →Why do cars commonly fail MOT tests?
Cars usually fail MOT tests because small problems build up throughout the year. A worn tyre, weak bulb, noisy brake or minor advisory can easily become a failure if it is ignored.
Wear and tear
Tyres, brakes, suspension bushes, wipers and lights naturally wear out with use.
Ignored advisories
Previous MOT advisories often become future failures if no repair is carried out.
Pothole damage
UK potholes can damage tyres, wheels, steering, suspension and alignment.
Electrical faults
Bulbs, sensors, wiring issues and dashboard warning lights can affect MOT results.
Rust and corrosion
Older cars can fail when corrosion affects structural or safety-related areas.
Poor maintenance
Skipped servicing can lead to brake, tyre, fluid, cooling and emissions problems.
Most common MOT failure reasons
1. Tyres
Tyres can fail an MOT for low tread depth, exposed cords, bulges, cuts, serious cracking or poor condition. Uneven tyre wear may also point to suspension or alignment problems.
Tyre MOT failure guide →2. Brakes
Brakes can fail because of worn pads, damaged discs, brake imbalance, weak braking force, warning lights, sticking calipers or leaking brake fluid.
Brake MOT failure guide →3. Lights
Headlights, brake lights, indicators, fog lights, side lights, rear lights and number plate lights must work correctly. Many light failures are simple but still cause MOT problems.
Lights MOT failure guide →4. Suspension
Broken coil springs, worn bushes, leaking shock absorbers, loose ball joints and knocking suspension parts are common MOT fail items.
Suspension MOT failure guide →5. Rust and corrosion
Surface rust is not always a fail, but serious corrosion near suspension, steering, braking or seatbelt mounting areas can fail an MOT.
Rust MOT failure guide →6. Emissions
A car can fail emissions for excessive smoke, engine faults, DPF problems, catalytic converter issues, exhaust leaks or poor engine running.
Emissions MOT failure guide →7. Warning lights
ABS, airbag, brake, ESC, traction control, TPMS and engine management lights can affect MOT results depending on the system and fault.
Engine management light MOT guide →8. Visibility issues
Wipers, washers, mirrors, windscreen damage and anything that affects the driver’s view can cause an MOT failure.
Windscreen chip MOT guide →Can warning lights fail an MOT?
Yes. Modern cars are controlled by electronic safety and emissions systems. If a warning light shows a fault with a safety system or emissions-related system, it can affect the MOT result.
- !ABS warning lights can fail an MOT.
- !Airbag or SRS warning lights can fail an MOT.
- !Brake warning lights should be checked immediately.
- !Engine management lights can affect emissions-related MOT results.
- !ESC and traction control faults may affect the MOT.
- !TPMS warning lights can affect newer vehicles where the system is fitted.
Items that can instantly fail an MOT
Some faults are serious enough to fail immediately because they affect road safety, visibility, emissions or the structure of the vehicle.
Dangerous tyres
Tyres below the legal tread limit, badly damaged tyres or exposed cords can fail immediately.
Brake defects
Poor braking force, severe imbalance or brake fluid leaks are serious MOT issues.
Major rust
Structural corrosion close to safety-related mounting points can be a serious failure.
Failed lights
Brake lights, headlights, indicators and number plate lights are common failure points.
Visibility problems
Large windscreen damage, failed wipers or no washer fluid can cause failure.
Warning lights
ABS, airbag, brake and emissions-related warning lights should be checked before the test.
Simple checks before your MOT
A basic check before the MOT can help you avoid simple failures. You do not need special tools for many of these checks.
- ✓Check all exterior lights, including brake lights and number plate lights.
- ✓Inspect tyre tread, sidewalls and overall tyre condition.
- ✓Test windscreen wipers and washer jets.
- ✓Look for dashboard warning lights before driving to the test.
- ✓Listen for grinding brakes, knocking suspension or humming wheel bearings.
- ✓Check for visible fluid leaks under the car.
- ✓Make sure number plates are readable and securely fitted.
- ✓Read your previous MOT advisories before booking the test.
For a fuller checklist, read our MOT preparation guide.
Why MOT history matters when buying a used car
MOT history can reveal how well a car has been looked after. Repeated advisories, corrosion warnings, tyre failures and brake issues can tell you a lot about the vehicle before you buy it.
- ✓Look for advisories that appear year after year.
- ✓Check carefully for corrosion history.
- ✓Watch for repeated tyre, brake or suspension failures.
- ✓Compare mileage records for unusual gaps or changes.
- ✓Be cautious if a car recently passed after several serious failures.
Useful guides: How to check MOT history, Used car inspection checklist, Buying a car with failed MOT history and Should you buy a car with advisories?.
Best mechanic-style advice before an MOT
If your car already feels wrong before the MOT, there is usually a reason. Grinding brakes, knocking suspension, steering vibration, overheating, smoke, strong exhaust smells or warning lights should not be ignored.
The best time to check the car is one or two weeks before the MOT, not on the morning of the test. That gives you time to sort simple problems before they become test-day failures.
Related MOT guides
Frequently asked questions
What are the most common MOT failures?
Tyres, brakes, lights, suspension, rust, warning lights, emissions faults and visibility problems are among the most common MOT failures.
Can warning lights fail an MOT?
Yes. ABS, airbag, brake, traction control, ESC, TPMS and engine management warning lights may affect MOT results depending on the vehicle and the fault.
Can I avoid an MOT failure?
Many MOT failures can be avoided by checking lights, tyres, wipers, washers, warning lights, number plates and obvious damage before the test.
Do advisories matter?
Yes. Advisories often become future MOT failures if ignored for another year.
What is the easiest MOT failure to avoid?
Faulty bulbs, empty washer fluid, damaged wipers, unreadable number plates and tyre pressure issues are among the easiest MOT failure risks to check before the test.
Can potholes cause MOT failures?
Yes. Potholes can damage tyres, wheels, steering, suspension and alignment. These issues can later show up during an MOT inspection.