The Most Common Reasons Cars Fail Their MOT

– And How To Prevent Them

Once a car in the UK is more than three years old, it must undergo an annual MOT test as required under the Road Traffic Act 1988.

The test, overseen by the Driver and Vehicle Standards Agency (DVSA), ensures vehicles meet legal standards for safety and environmental performance. Despite this being a routine process, a significant number of cars fail on their first attempt each year. The majority of these failures are not the result of complex faults but of issues that drivers can check and resolve beforehand.

Below are the most frequent reasons vehicles fail their MOT, along with straightforward steps to help prevent them.

 

Lighting And Indicators

Problems with vehicle lighting are the leading cause of MOT failures. This includes headlights, brake lights, indicators, rear lights, and number plate illumination. The test requires all lights to function correctly, be secure, and positioned properly.

A simple check before booking your MOT is effective. Switch on each set of lights and walk around the vehicle. Enlist someone to confirm brake and reverse lights. Replacement bulbs are inexpensive and widely available.

 

Tyres

Tyres must meet a legal minimum tread depth of 1.6mm across the central three-quarters of the tyre. They must also be free of cuts, bulges, or other structural damage. Many MOT failures occur because tyres fall below this standard.

A quick method is to use a 20p coin: place it into the tread. If the coin’s border is visible, the tyre is worn and must be replaced. Tyre pressure should also be checked regularly to avoid uneven wear.

 

Brakes

Brake performance is measured during the MOT, and worn or damaged components regularly lead to failures. Pads, discs, and fluid levels are all checked.

If you notice unusual noises, vibration when braking, or reduced responsiveness, book an inspection in advance of your MOT. Addressing brake issues early avoids both failure and increased repair costs.

 

Wipers And Washers

Windscreen wipers and washers are required to provide a clear view of the road. Blades that leave streaks or fail to clear water are a common reason for a fail, as is an empty washer reservoir.

Before the test, top up the washer fluid and replace worn blades. Both are low-cost tasks that can prevent your car from being marked down.

 

Suspension

Suspension faults such as broken springs, leaking shock absorbers, or excessive wear in joints are regularly identified in MOT tests. These issues affect stability and handling, making them a safety concern.

Warning signs include knocking noises when driving over uneven roads or the car sitting lower on one side. If these symptoms are present, have the system inspected before the test.

 

Exhaust And Emissions

Exhaust systems are inspected for leaks, noise levels, and emissions. Diesel cars are subject to stricter standards, and the absence or tampering of a diesel particulate filter (DPF) is an automatic fail. Excessive smoke or emissions will also lead to rejection.

Maintaining the engine properly, ensuring the oil is changed regularly, and addressing performance issues promptly helps reduce the risk of an emissions fail.

 

Seatbelts And Restraints

Seatbelts are checked to confirm they latch securely, retract correctly, and are free from cuts or fraying. Any fault with a seatbelt is recorded as a failure.

Carry out a quick inspection: pull the belt out fully to check for damage, then tug firmly to confirm the locking mechanism engages.

 

Registration Plates

Number plates must comply with DVLA standards in terms of font, spacing, visibility, and condition. Plates that are dirty, cracked, or obscured are a common reason for MOT failure.

Clean both plates before the test and replace any that are damaged.

 

Steering

The steering system is examined for excessive play, leaks, or worn components. Any fault that affects vehicle control will result in a fail.

Difficulty turning the wheel or noises while steering should be investigated in advance. Routine servicing often picks up these issues before they develop further.

 

Visibility

Beyond the windscreen, visibility includes mirrors and windows. Cracked mirrors, tinted windows that exceed legal limits, or stickers that block the driver’s line of sight will all cause problems in the test.

Replacing mirror glass or removing obstructions is inexpensive and can be resolved quickly.

 

Fail To Prepare, Prepare To Fail

The majority of MOT failures result from issues that are easy to check and resolve in advance. Taking time to look over your vehicle before the test can save money and avoid disruption.

Driving without a valid MOT certificate, except when travelling to a pre-booked appointment, is against the law. Penalties include fines of up to £1,000 and the possibility of invalidated insurance.

The MOT is not a substitute for regular servicing. It provides assurance that your vehicle meets the minimum legal standards for road safety and emissions. Addressing problems early and maintaining your vehicle throughout the year reduces the likelihood of a failed test and helps ensure your car remains safe and compliant on the road.