What Are The Most Common MOT Failure Reasons?
Warning lights, tyre damage, brake noise, heavy smoke, suspension knocking, poor braking performance 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, faulty bulbs, damaged wipers, dashboard warning lights, brake noise, knocking suspension, fluid leaks, heavy exhaust smoke and visible corrosion.
Major Defect
A major defect means the vehicle does not meet the MOT standard and must be repaired before a pass certificate can be issued.
Dangerous Defect
A dangerous defect means the car is unsafe to drive. Repairs should be completed before the vehicle is used again.
Advisory Item
An advisory is not a failure, but it warns that a component is worn, deteriorating or likely to need attention later.
If your previous MOT included brake, tyre, suspension, corrosion or emissions advisories, inspect those areas before the next test. Repeated advisories often turn into future MOT failures if ignored.
Detailed MOT Failure, Advisory & Roadworthiness Guides
This page is the main hub for common MOT failure reasons in the UK. Use the guides below to understand why cars fail MOT tests, how advisories become future failures, what faults affect roadworthiness and which problems should be repaired before test day.
A failed MOT is not always a surprise. Brake wear, tyre damage, corrosion, warning lights and suspension problems often appear first as MOT advisories. If the same advisory appears year after year, treat it as a future failure risk.
Brake MOT Failures
Worn brake pads, brake imbalance, damaged discs, brake fluid leaks, ABS faults and parking brake issues explained.
Tyre MOT Failures
Low tread, sidewall damage, bulges, exposed cords, uneven wear and tyre pressure warning issues explained.
Light MOT Failures
Headlights, brake lights, indicators, fog lights, number plate lights, cracked lenses and alignment issues explained.
Suspension MOT Failures
Broken springs, worn bushes, leaking shocks, ball joints, anti-roll bar links and knocking suspension explained.
Rust MOT Failures
Sill rust, chassis corrosion and corrosion near suspension, steering, braking or seatbelt mounting points explained.
Emissions MOT Failures
Excessive smoke, DPF problems, catalytic converter faults, exhaust leaks, lambda sensors and engine warning lights explained.
MOT Advisories Explained
Understand what MOT advisories mean, how serious they are, whether you can drive and when they become expensive.
MOT Advisory Meaning
Learn the difference between advisories, minor defects, major defects and dangerous MOT defects.
Corroded Brake Pipe Advisory
Brake pipe corrosion is one of the most important advisories to understand because it can become a serious brake failure.
Driving With An Advisory
Find out how long you can drive with an MOT advisory and when you should repair it before the next test.
Brake System Knowledge
Brake failures often involve pads, discs, calipers, brake fluid, pipes, ABS or electronic parking brake faults.
Used Car MOT Checks
A used car with repeated MOT failures or advisories should be inspected carefully before purchase.
Start with the failure category that matches your MOT sheet, then check the advisory history. If the same fault area appears repeatedly, such as brakes, tyres, corrosion or suspension, assume the car may need repair before the next MOT.
MOT Legal Rules After Failure or Expiry
An MOT failure is more than a repair issue—it can affect whether your vehicle can legally be driven, where it may be parked, your insurance cover, road tax, police enforcement and your responsibilities as the registered keeper. The guides below explain the legal rules every UK driver should understand after an MOT failure or expiry.
A failed MOT does not automatically make a vehicle illegal to own, but a vehicle with a dangerous defect should not be driven on the road. Driving an unsafe vehicle can lead to prosecution, invalidate insurance in some circumstances and place other road users at risk.
What Happens If Your Car Fails MOT?
Understand major defects, dangerous defects, MOT retests, repair options and what happens after receiving an MOT failure certificate.
Can You Drive A Car With A Failed MOT?
Learn when driving may still be legal, when it is prohibited and how dangerous defects affect road use.
Driving With An Expired MOT
Understand fines, penalty points, insurance implications and the legal exemptions for travelling to a pre-booked MOT test.
Can Police Check Your MOT?
Learn how police officers use DVSA records and Automatic Number Plate Recognition (ANPR) to identify vehicles without a valid MOT.
Parking Without A Valid MOT
Find out whether a vehicle without a valid MOT can be parked on a public road and what alternatives are available.
SORN, Insurance & MOT
Understand how SORN affects insurance, MOT requirements, vehicle tax and returning your vehicle to the road legally.
If your vehicle has failed its MOT, first understand the type of defect recorded on the MOT certificate. Next, check whether the vehicle can legally be driven, arrange any necessary repairs and book a retest. If the vehicle has a history of repeated advisories or failures, review its previous MOT history before deciding whether further repairs are worthwhile.
Why Do Cars Commonly Fail MOT Tests?
Most MOT failures are not caused by sudden mechanical breakdowns. Instead, they develop gradually through normal wear and tear, ignored MOT advisories, poor maintenance or damage caused by everyday driving. Understanding why vehicles fail MOT tests helps drivers identify problems earlier, reduce repair costs and improve the chances of passing the next inspection.
Many vehicles fail the MOT because the same advisory appears year after year without being repaired. Worn brake pads become brake failures, tyre advisories become illegal tyres, while minor corrosion can eventually become structural rust that results in an MOT failure.
Normal Wear & Tear
Brake pads, brake discs, tyres, suspension components, wiper blades and light bulbs gradually wear during normal driving and eventually fall below MOT standards.
Ignored MOT Advisories
Many MOT failures begin as advisories. Repeated advisories for brakes, tyres, suspension or corrosion should always be repaired before the next MOT test.
Pothole & Kerb Damage
Potholes and kerb impacts can damage tyres, alloy wheels, steering components, suspension parts and wheel alignment, increasing the likelihood of an MOT failure.
Electrical & Warning Light Faults
Dashboard warning lights, ABS faults, traction control issues, electronic parking brake faults, faulty sensors and damaged wiring can all contribute to MOT failures.
Rust & Structural Corrosion
Corrosion affecting chassis rails, suspension mounting points, brake pipes or seat belt anchorages is one of the most serious MOT failure categories on older vehicles.
Poor Maintenance
Delayed servicing, neglected repairs and ignoring unusual noises or warning lights often allow small faults to develop into expensive MOT failures.
A simple pre-MOT inspection can identify many common faults before the test. Check tyres, brakes, lights, windscreen wipers, fluid levels, dashboard warning lights and any previous MOT advisories. Catching problems early is usually far cheaper than repairing major MOT failures after the inspection.
Most Common MOT Failure Reasons
Most MOT failures fall into a small number of repeat categories. Tyres, brakes, lights, suspension, corrosion, emissions, warning lights and visibility problems are among the areas drivers should check before test day.
1. Tyres
Tyres can fail for low tread depth, exposed cords, bulges, cuts, serious cracking or poor condition. Uneven tyre wear may also point to suspension, tracking or alignment problems.
2. Brakes
Brakes can fail because of worn pads, damaged discs, brake imbalance, weak braking force, ABS faults, sticking calipers, parking brake problems or leaking brake fluid.
3. Lights
Headlights, brake lights, indicators, fog lights, side lights, rear lights and number plate lights must work correctly. Many light failures are simple checks before the test.
4. Suspension
Broken coil springs, worn bushes, leaking shock absorbers, loose ball joints, anti-roll bar links and knocking suspension parts are common MOT fail items.
5. Rust & Corrosion
Surface rust is not always a failure, but serious corrosion near suspension, steering, braking, chassis or seatbelt mounting areas can fail an MOT.
6. Emissions
A car can fail emissions for excessive smoke, engine faults, DPF problems, catalytic converter issues, exhaust leaks, lambda sensor faults or poor engine running.
7. Warning Lights
ABS, airbag, brake, ESC, traction control, TPMS and engine management lights can affect MOT results depending on the system and fault present.
8. Visibility Issues
Wipers, washers, mirrors, windscreen damage and anything that affects the driver’s view can cause an MOT failure.
9. Ignored Advisories
Repeated MOT advisories for brakes, tyres, suspension, corrosion or leaks often become future failures if they are not repaired.
Start with tyres, lights, brakes and warning lights because these are easy to check before the test. Then review the previous MOT history for repeated advisories, especially for brakes, suspension, corrosion and emissions faults.
Can Dashboard Warning Lights Cause an MOT Failure?
Modern vehicles constantly monitor braking, steering, stability, emissions and occupant safety systems. During the MOT inspection, certain warning lights are checked because they indicate faults affecting roadworthiness or emissions compliance. Not every illuminated warning light automatically results in an MOT failure, but many safety-related systems do.
If a warning light indicates a fault with a mandatory safety system or emissions control system, the vehicle may fail its MOT. Always diagnose warning lights before booking the test rather than assuming they can be ignored.
Dashboard Warning Light MOT Decision Guide
ABS Warning Light
An illuminated ABS warning light normally results in an MOT failure because the Anti-lock Braking System is a mandatory safety feature.
ABS Explained →Brake Warning Light
Brake hydraulic faults, low brake fluid or parking brake faults should always be investigated before driving or presenting the vehicle for an MOT.
Brake Warning Light Guide →Electronic Parking Brake
Electronic Parking Brake faults may prevent correct parking brake operation and often require diagnosis before the vehicle can pass its MOT.
Electronic Parking Brake Fault →Traction Control
Traction control faults are frequently linked with ABS or stability control faults and should always be investigated before the MOT.
Traction Control Warning Light →Airbag / SRS
An illuminated SRS warning light usually indicates a fault with the supplemental restraint system and is normally an MOT failure.
Airbag Warning Light MOT Guide →Engine Management Light
Engine management faults affecting emissions performance can lead to an MOT failure, particularly if emissions exceed legal limits.
Engine Management Light MOT Guide →ESC / Stability Control
Electronic Stability Control faults may affect the MOT depending on the vehicle and the system reporting the fault.
ESC Warning Guide →TPMS Warning Light
Where a Tyre Pressure Monitoring System is fitted as standard, an illuminated TPMS warning light may result in an MOT failure.
TPMS Guide →Multiple Warning Lights
Several warning lights appearing together often indicate a shared electrical, ABS or CAN Bus fault requiring diagnostic equipment.
Vehicle Diagnostics →ABS, traction control and electronic parking brake faults frequently appear together because these systems share wheel speed sensors, control modules and braking components. Diagnosing the root cause before replacing parts can save hundreds of pounds in unnecessary repairs.
Items That Can Instantly Fail an MOT
Some defects are considered serious enough to result in an immediate MOT failure because they directly affect vehicle safety, roadworthiness or environmental standards. Identifying these faults before your MOT can save both repair costs and the inconvenience of a failed test.
Dangerous Tyres
Tyres below the legal 1.6 mm tread depth, exposed cords, sidewall bulges, deep cuts or severe damage will normally fail an MOT immediately.
Tyre MOT Failure Guide →Brake Defects
Worn brake pads, damaged discs, sticking calipers, hydraulic leaks, brake imbalance or poor braking efficiency are among the most common MOT failures.
Brake MOT Failure Guide →Structural Corrosion
Serious corrosion affecting suspension, steering, braking components or seat belt mounting points can result in an immediate MOT failure.
Rust MOT Failure Guide →Lighting Defects
Faulty headlights, brake lights, indicators, rear lamps, fog lights or number plate lights are frequent reasons for MOT failure.
Lighting MOT Failure Guide →Visibility Problems
Large windscreen chips, ineffective wipers, empty washer reservoir or damaged mirrors can all lead to an MOT failure.
Windscreen MOT Guide →Dashboard Warning Lights
ABS, brake, airbag, engine management and other mandatory system warning lights can all affect the MOT outcome depending on the fault present.
Dashboard Warning Lights Guide →Excessive Emissions
DPF faults, catalytic converter problems, excessive exhaust smoke and poor emissions readings are common reasons for failing an MOT emissions test.
Emissions MOT Failure Guide →Ignored MOT Advisories
Many failed MOT tests begin as advisories on the previous inspection. Fixing advisory items early greatly reduces the chance of failing next year.
Most Common MOT Advisories →Suspension & Steering
Broken springs, worn bushes, leaking shock absorbers, loose ball joints and steering defects frequently result in MOT failures.
Suspension MOT Failure Guide →Most immediate MOT failures do not happen overnight. Worn tyres, noisy brakes, suspension knocks, illuminated warning lights and MOT advisories usually provide weeks or even months of warning before the vehicle reaches the point of failure. Carrying out regular inspections and repairing advisory items promptly is often the cheapest way to avoid an unexpected MOT failure.
Simple Checks Before Your MOT Test
Many MOT failures are caused by faults that can be identified in just a few minutes at home. Carrying out these simple checks before your appointment can improve your chances of passing first time, reduce unexpected repair bills and highlight previous MOT advisories that still require attention.
Lighting
Walk around the vehicle and check that all headlights, side lights, brake lights, indicators, reversing lights, rear fog lights and number plate lights are working correctly.
Lighting MOT Guide →Tyres
Inspect tyre tread depth, sidewalls, cuts, bulges, exposed cords and uneven wear. Also check tyre pressures before travelling to the MOT station.
Tyre MOT Guide →Brakes
Listen for grinding noises, squealing, vibration or pulling under braking. Ensure the brake warning light switches off after starting the engine.
Brake MOT Guide →Visibility
Check windscreen wipers, washer jets, mirrors and inspect the windscreen for damage within the driver's field of vision.
Windscreen MOT Guide →Dashboard Warning Lights
Start the engine and confirm that ABS, airbag, brake, engine management and other safety warning lights extinguish normally.
Warning Lights Guide →Previous MOT Advisories
Review your last MOT certificate and repair any advisory items before they become major or dangerous defects during the next inspection.
MOT Advisories Explained →- ✓Test every exterior light, including brake lights, indicators and number plate lights.
- ✓Inspect tyre tread depth, condition and inflation.
- ✓Check windscreen wipers, washer jets and mirrors.
- ✓Confirm all dashboard warning lights switch off correctly.
- ✓Listen for brake noise, suspension knocks or steering issues.
- ✓Look underneath the vehicle for oil, coolant or brake fluid leaks.
- ✓Ensure number plates are clean, secure and easy to read.
- ✓Review previous MOT advisories and repair outstanding defects.
Many drivers focus only on obvious faults before an MOT, but checking your previous MOT advisories can be just as important. Advisories for tyres, brakes, suspension, corrosion or fluid leaks often develop into major defects if left unrepaired. Spending a few minutes inspecting your vehicle before the test can significantly improve the chances of a first-time pass.
For a complete inspection routine, read our How to Prepare for an MOT Test guide, then review Most Common MOT Advisories Explained to understand which advisory items are most likely to become future MOT failures.
Why MOT History Matters When Buying a Used Car
An MOT certificate only shows whether a vehicle passed or failed on the day of the inspection. The complete MOT history tells a much bigger story, revealing how well the vehicle has been maintained, whether faults have been repaired properly and if the same problems continue to appear year after year. Reviewing this history before buying a used car can help you avoid expensive repairs and identify vehicles that may have been poorly maintained.
A vehicle with one or two minor advisories is not necessarily a poor purchase. However, repeated advisories for brakes, tyres, suspension, corrosion, steering or fluid leaks often suggest maintenance has been delayed and further repairs may soon be required.
Repeated MOT Advisories
Look for advisory items that appear on several consecutive MOT certificates. Repeated advisories often become future MOT failures if they remain unrepaired.
Brake & Suspension History
Repeated failures for brakes, suspension or steering components may indicate neglected servicing or expensive repairs in the near future.
Corrosion Records
Structural corrosion advisories should never be ignored. Check underneath the vehicle carefully if rust appears repeatedly in the MOT history.
Mileage Consistency
Compare recorded MOT mileages to identify unusual gaps, unexplained reductions or long periods with very little vehicle use.
Recent MOT Pass
A recent MOT pass is positive, but always review previous failures and advisories to understand the vehicle's long-term maintenance history.
Complete Vehicle Inspection
Never rely solely on the MOT history. Combine it with a thorough inspection, service records and a road test before buying.
- ✓Have the previous MOT advisories been repaired?
- ✓Has the vehicle repeatedly failed on the same components?
- ✓Is there evidence of structural corrosion or brake pipe advisories?
- ✓Do the MOT mileage records match the service history?
- ✓Has the vehicle passed immediately each year or required repeated retests?
- ✓Are there invoices proving advisory items have been repaired?
Continue your research with our complete buying guides: How to Check MOT History Before Buying a Car, Used Car Inspection Checklist, Buying a Car With Failed MOT History, Should You Buy a Car With MOT Advisories? and Used Car Buying Guides Hub.
Mechanic's Advice Before Taking Your Car for 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 dashboard warning lights should not be ignored. These symptoms often point to faults that may become MOT failures if left unchecked.
The best time to inspect the vehicle is one or two weeks before the MOT, not on the morning of the test. This gives you time to repair simple faults, investigate previous advisories and avoid last-minute garage pressure.
Listen To The Car
Grinding brakes, suspension knocks, steering vibration, exhaust noise and warning lights are often early signs of MOT failure risks.
Check Previous Advisories
Repeated advisories for brakes, tyres, corrosion or suspension often become future MOT failures if ignored.
Repair Small Faults Early
Bulbs, wipers, washer fluid, number plates and tyre pressure are simple checks that can prevent avoidable MOT failures.
A fresh MOT pass does not mean a car is perfect. It only means the vehicle met the minimum legal roadworthiness standard at the time of inspection. Always read the advisory section carefully and repair repeated advisories before they become expensive failures.
Explore The Complete MOT Knowledge Centre
Continue through the Motor Vehicle Expert MOT guides to understand failure reasons, advisories, retest rules, legal driving rules, road tax, insurance, used car checks and repair priorities.
MOT Failure Guides
MOT Advisory Guides
Brake & Safety Advisories
Legal MOT Rules
Tax, Insurance & Ownership
Used Car MOT Checks
Frequently Asked Questions About MOT Failures
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, previous advisories and obvious damage before the test.
Do MOT advisories matter?
Yes. Advisories often become future MOT failures if ignored for another year, especially advisories for brakes, tyres, suspension, corrosion or leaks.
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 appear during an MOT inspection.