Top 5 Reasons Your Car Might Fail Its MOT in High Wycombe (And How to Avoid Them)

If you own a vehicle in High Wycombe, an MOT test is one of the most important annual checks to keep your car road-legal and safe. But what happens if it fails? More importantly, what are the most common reasons cars fail their MOT, and how can you avoid costly retests?

At High Wycombe MOT Centre, we perform thousands of MOT tests every year, and we’ve seen just about every reason for failure. In this guide, we’ll share the top 5 MOT failure reasons, what they mean, and practical steps to help you avoid them. Whether you’re prepping your car for its test or checking up after a fail, this article will help you make informed decisions and stay compliant.

What Is an MOT & Why Do Cars Fail It?

The MOT test is a legal requirement in the UK for most vehicles over three years old. It checks the safety, roadworthiness, and emissions standards set by the DVSA. Failures can range from minor defects to serious safety risks that prevent your car from being driven legally.

The most common MOT failures often relate to lighting issues, tyre safety, brake wear, emissions, and visibility concerns. Some of these problems are simple to fix with regular vehicle checks, while others may require diagnostics or parts replacement. Knowing what to expect can save you hassle on the day of your test.

What Are the Top 5 Reasons for MOT Failures?

1. Faulty or Inadequate Lighting

Lights are one of the most frequent causes of MOT failure, largely due to blown bulbs, cracked lenses, or misaligned beams. Since lighting affects both your visibility and how visible you are to other road users, even a minor defect can result in a fail.

Tip: Test your headlights, indicators, brake lights, and number plate lights regularly. Replace any faulty bulbs promptly.

2. Worn or Unsafe Tyres

Your tyres must meet strict requirements to pass an MOT. If the tread depth falls below 1.6mm, or if tyres show signs of damage like bulges, cracks, or uneven wear, your vehicle will not pass. Under-inflated tyres can also contribute to uneven tread.

Tip: Use a 20p coin to check tread depth. If the outer rim is visible, your tyres need replacing.

3. Brake Issues

Brakes are critical for safety and will be closely examined during the MOT. Worn brake pads, uneven braking performance, low brake fluid, or corrosion on discs can all lead to a fail.

Tip: If you notice your car pulling to one side, a soft brake pedal, or unusual noises when braking, book a check-up before your test. We also offer full brake repair services at our High Wycombe garage.

4. Poor Emissions Performance

The emissions test ensures your vehicle meets environmental regulations. Excess smoke, a failed lambda reading, or high CO2 levels can trigger a fail. Common causes include faulty oxygen sensors, dirty air filters, or a malfunctioning EGR valve.

Tip: Use a fuel additive a week before your MOT and take your car on a longer drive to clear the exhaust system.

5. Cracked Windscreens or Faulty Wipers

Your windscreen must offer a clear and unobstructed view. Cracks larger than 10mm in the driver’s line of sight or over 40mm elsewhere can lead to failure. Wipers must effectively clear water without leaving streaks or smears.

Tip: Replace worn wiper blades every 6–12 months and address chips in the windscreen before they spread.

How to Prepare Your Car to Pass Its MOT First Time

Being proactive about car care is the best way to avoid surprises. Before your test:

• Do a walk-around check: test lights, horn, wipers, mirrors, and indicators.
• Check tyres for wear, damage, and pressure.
• Top up fluids: oil, brake fluid, coolant, screenwash.
• Look for dashboard warning lights and resolve any issues.
• Book a pre-MOT inspection with our team if in doubt.

What to Do If Your Car Fails Its MOT

If your vehicle fails its MOT, you’ll receive a VT30 fail certificate. This outlines the faults that need to be addressed before a retest.

At High Wycombe MOT Centre:

• We offer on-site repairs and servicing and retests within 10 working days.
• You’ll receive a transparent quote for any necessary work.
• We can often fix issues same-day to minimise downtime.

FAQs About MOT Failures

Can you drive a car with a failed MOT?

No, unless you’re driving to a pre-booked MOT or repair appointment. Otherwise, it’s illegal and may invalidate your insurance.

My car failed its MOT on emissions. What can I do?

Book a diagnostic check. The issue may involve the exhaust, sensors, or air intake. We can help identify and repair it.

How much does an MOT retest cost?

Retests are free within 10 working days if repairs are completed on-site. Otherwise, a partial fee may apply.

Can minor issues cause an MOT fail?

Yes. Even simple problems like worn wiper blades or number plate light failures can result in a fail if they affect safety or visibility.

What happens if I ignore an MOT failure?

Your vehicle is no longer road-legal. Driving it could result in fines, points, or even prosecution. You must repair and retest before driving again.

Pass Your MOT First Time with Expert Help

Don’t let small faults lead to an MOT failure. At High Wycombe MOT Centre, we offer expert pre-checks, diagnostics, and fast repairs to keep you on the road. 

Book online today or call 01494 952678.

We’re here to help you pass the first time, every time.