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Common MOT Faults: Minor, Major & Dangerous Defects Explained

09/05/202506/04/2026 Harris Cumming

Help & Advice

Common MOT Faults: Minor, Major & Dangerous Defects Explained

No one looks forward to an MOT failure – it often means facing an unexpected and unwelcome expense.

Knowing what can potentially fail your MOT is important, as it can better prepare you for your upcoming test – whether that’s in 2 weeks or 2 months – by giving you time to address any issues early and avoid unnecessary surprises or delays.

In this guide, we’ll break down the most common MOT faults, explain the difference between minor, major, and dangerous defects, and help you understand what each type means for your vehicle.

Defect Categories Explained

When your vehicle undergoes an MOT test, any faults found are grouped into one of three defect categories: minor, major, or dangerous.

These categories help determine whether your vehicle passes or fails, and what actions are needed next.

Here's what each one means:

Minor

Minor MOT defects are the smaller issues that aren’t serious enough to fail your MOT, but they’re still worth keeping an eye on.

Think of them as mini warning signs that something might need attention soon, even if it’s not causing immediate concern.

For example, a worn tyre tread that’s still above the legal limit, or a windscreen washer that’s not spraying strongly, could be flagged as minor.

Your car will still pass the test, but these faults will be recorded on the certificate, so it’s a good idea to get them sorted before they turn into bigger problems.

Major

Major defects are more serious – they mean your car has failed its MOT.

These faults usually have a direct impact on safety, emissions, or overall roadworthiness.

A brake imbalance, headlight failure, or a tyre below the legal tread depth are common examples.

Even though they might not stop your car from moving, they compromise how safely it can operate.

So, if you get a major fault and your vehicle is deemed not roadworthy, you’ll need to get it repaired and then retested before you’re back on the road.

Dangerous

Dangerous defects are exactly what they sound like – faults that make your vehicle unsafe to drive.

If something is flagged as dangerous, you’re not just failing the MOT, you’re also legally prohibited from driving the car until the issue is fixed.

It could be something like severely worn brakes, a steering system fault, or leaking hydraulic fluid. These kinds of problems put both you and other road users at risk.

If you’re given a dangerous defect, the garage won’t let you take the car away unless it’s on a recovery truck – and honestly, it’s for good reason.

Common Minor Faults

The following are common minor faults that don’t cause a fail but still deserve a spot on your radar:

Minor Fault	Description
Windscreen Washer Not Spraying Properly	If the windscreen washer jets are clogged or the fluid level is low, you’ll still pass – but it’s a quick fix that keeps your view clear in bad weather.
Worn Wiper Blades	Wipers that leave streaks or miss patches on the windscreen are noted as minor. They’re cheap to replace and worth fixing before comprising weather conditions.
Slightly Worn Tyres (Above Legal Limit)	Tyres that are close to the 1.6mm tread depth minimum might not fail you just yet, but they’ll be flagged for replacement soon.
Cracked Number Plate (Still Readable)	If your number plate is cracked but all the characters are visible and correctly spaced, it’s a minor issue. However, it’s worth replacing before it worsens.
Faded or Slightly Damaged Reflectors	If your rear reflectors are a bit cloudy or chipped but still do their job, it’ll be classed as a minor defect.
Loose or Noisy Exhaust Mounts	Your exhaust might rattle slightly due to a worn mount – not dangerous, but it can be a sign of wear worth getting checked.
Minor Fluid Leaks (Not Dripping)	Slight misting around pipes or joints might be picked up, but if nothing’s actively leaking or dripping, it’s just a note for your attention.
Loose Trim or Panels	Exterior trim that’s starting to come loose but isn’t in danger of falling off will usually be marked as minor.

Common Major Faults

The below issues might not be outright dangerous yet, but they’re serious enough to fail your MOT and will need fixing before your car can hit the road again:

Major Fault	Description
Tyres Below the Legal Tread Depth	If any tyre is below 1.6mm of tread, it’s a straight fail. It affects braking and grip in wet and dry conditions, meaning it comprises safety.
Brake Pad Wear Beyond the Limit	Pads that are too thin won’t give you the stopping power you need. Even if your brakes feel okay, they’re no longer up to standard and will fail.
Broken or Faulty Headlights	If your dipped or main beam isn’t functioning properly, you’ll fail your MOT test.
Suspension Wear or Damage	Worn-out springs, bushes, or shock absorbers will earn you a major defect. Suspension problems can affect both handling and comfort.
Handbrake Not Holding Properly	A handbrake that doesn’t keep the car still on a slope is a safety issue – especially if you park on hills regularly.
Excessive Emissions	A fail will occur if your car is emitting more CO2 or other pollutants than allowed.
Steering Rack Issues	Loose or leaking steering components can compromise control and need immediate attention.
Sharp Edges from Exterior Damage	If rust or damage has left sharp edges exposed, that’s a major defect – it could be hazardous to others, even if your car drives fine.
Brake Fluid Leaks	Any sign of fluid escaping from the brake system will lead to a fail – braking performance can drop off fast with low fluid levels.
Indicators Not Working	If one or more indicators aren’t functioning correctly, that’s a major issue. Drivers and pedestrians rely on these to know your intentions.

Common Dangerous Faults

If any of these come up in your MOT, your car fails instantly, and you can’t legally drive it until it’s fixed:

Dangerous Fault	Description
Severely Worn or Exposed Tyres	Bald patches, cords showing, or sidewall damage make tyres unsafe. Tyre blowouts at speed are highly dangerous.
Brakes Not Working or Severely Worn	If one or more brakes aren’t functioning properly, or if the pedal goes to the floor, the car is considered a serious risk on the road.
Steering Completely Loose or Unresponsive	If the steering has excessive play or parts have broken loose, the driver could lose control entirely – it’s a serious safety concern.
Leaking Fuel System	Any smell of fuel or signs of leaking petrol or diesel is a major hazard – it’s both a fire risk and dangerous for other road users.
Dangerous Corrosion on Suspension or Chassis	Rust that affects the vehicle’s structure, especially around mounting points or key load-bearing areas, makes the vehicle unsafe. This is particularly dangerous in an accident.
Missing or Broken Seatbelts	If seatbelts are frayed, missing, or don’t latch securely, it puts occupants at risk – especially in an accident.
Blown-Out or Cracked Brake Pipes	Brake pipes under pressure can burst if cracked or heavily corroded, which means no braking when you need it most.
Suspension Springs Snapped or Detached	If a spring is broken or out of place, your handling and control are severely affected – it’s a major road safety risk.
Completely Failed Lighting Systems	If all front or rear lights are out, or the vehicle can’t be seen in poor visibility, it’s too dangerous to be on the road.
Wheels Not Securely Attached	Loose wheel nuts or damaged hubs that risk a wheel detaching while driving will be marked as dangerous without question.

I’ve Failed My MOT, What Now?

Failing your MOT can be frustrating, especially if it’s caught you off guard – but what actually happens next depends on why your car failed and whether your current MOT certificate is still valid.

If your car is given major defects, it fails the test but may still be driven, as long as your existing MOT hasn’t expired and the vehicle is deemed roadworthy. This gives you a little breathing room to get the necessary repairs sorted and then bring it back for a partial retest.

However, if your car receives a dangerous defect, that’s a different story. It means the vehicle isn’t safe to be on the road, and by law, you can’t drive it away – even if your old MOT certificate is still technically in date. In these cases, your best option is to leave the car at the test centre for repair, or have it transported on a recovery truck.

While an MOT failure isn’t ideal, it’s designed to flag up safety issues before they become real problems. Getting repairs done promptly not only helps you pass your retest but also ensures your car is safe, legal, and ready for the road.

MOT Faults: Frequently Asked Questions

How many majors fail an MOT?

A single major or dangerous defect will result in an MOT failure.

Can I drive with a major MOT defect?

A vehicle that fails its MOT due to a major defect may still be driven if its current MOT remains valid and it is considered roadworthy. The defect must be fixed without delay.

If car fails MOT how long do I have to fix it?

Following an MOT failure, you may have up to 10 working days to return to the same test centre for a free or reduced-fee retest. Vehicles with dangerous defects must not be driven, while those with major defects may only be driven to a place of repair.

How many minor defects to fail mot?

A vehicle can still pass its MOT with any number of minor defects. These issues don’t pose an immediate risk to safety or the environment, but they are recorded on the certificate and should be repaired as soon as possible to prevent future failures.