MOT Fail Codes Explained: Major Defects vs. Minor Issues

An MOT (Ministry of Transport) test is essential for ensuring the safety, roadworthiness, and environmental standards of vehicles in the UK.

If your car fails its MOT, it can be a stressful experience, especially if you don’t understand what the fail codes mean.

MOT failures are categorized into major defects and minor issues.

Understanding the difference between these two can help you decide the urgency of repairs and whether you can still drive your vehicle.

What is an MOT?

The MOT test is a legal requirement for vehicles over three years old. It ensures that the vehicle meets road safety and environmental standards. The test covers various aspects of the car, including lights, brakes, exhaust emissions, and structure.

If your vehicle fails the MOT, the tester will provide a list of issues, categorized as either major defects or minor issues.

MOT Fail Codes: Major Defects vs. Minor Issues

Major Defects:
Major defects are serious issues that compromise the safety of your vehicle or the environment. If a major defect is found, your car will fail the MOT test. A major defect means the vehicle is unsafe to drive, and in most cases, you will not be allowed to drive it away from the testing station unless you have a pre-arranged appointment for repairs.

Minor Issues:
Minor issues are problems that do not pose an immediate safety risk but should still be addressed as soon as possible. These issues will not result in a fail, but they will be recorded as advisories. You can continue driving your car with minor issues, but you should aim to resolve them before your next MOT.

Major Defects: Common Fail Codes

1. Brakes
   • Brakes not working efficiently: A major defect. This can include worn brake pads, damaged brake discs, or air in the brake lines.
   • Brake fluid leaks: If fluid is leaking from any part of the braking system, it is a serious safety issue.
   • Handbrake not functioning: A faulty handbrake is considered a major defect, especially if it’s unable to hold the vehicle stationary.
   Cost: Brake repairs can vary significantly, but replacing brake pads typically costs £100 to £200, while full brake disc replacements can reach £300 to £500.
2. Lights and Indicators
   • Faulty headlights: If headlights are misaligned, broken, or do not work, it’s a major defect. Poor lighting is a direct safety concern.
   • Broken indicators: A failure to indicate properly, whether the bulb is broken or the wiring is faulty, can lead to a fail.
   cost: Replacing a headlight or indicator bulb can cost between £10 and £40. However, if the wiring or electrical components are damaged, the cost could rise to £100 to £150.
3. Suspension
   • Damaged suspension components: Broken or worn suspension parts like shock absorbers or springs will cause your car to fail the MOT. This affects handling and safety.
   • Uneven or excessive play: If the suspension system has too much movement, it indicates a serious fault that requires immediate attention.
   Cost: Suspension repairs typically range from £100 to £500 depending on the parts needed and labor time.
4. Tyres
   • Tyre tread depth below 1.6mm: If the tread on any of your tyres is too low, your vehicle will fail the MOT. Tyres are a vital part of road safety.
   • Tyre damage: Cuts or bulges on the tyres are also classified as major defects.
   Cost: Replacing a tyre can cost between £50 and £150, depending on the brand and vehicle model.
5. Exhaust System
   • Excessive emissions or exhaust leaks: If the exhaust system is leaking or emitting excessive smoke, it’s a major defect.
   • Damaged or rusted exhaust components: A damaged exhaust could lead to harmful emissions, which affect the environment.
   Cost: Replacing a section of the exhaust system can cost between £100 and £400, depending on the repair.

Minor Issues: Common Fail Codes

1. Windshield Wipers
   • Wiper blades worn or damaged: If your wiper blades are leaving streaks or are cracked, it’s a minor issue.
   • Inoperative washers: The windscreen washers should be functioning correctly, but a minor issue may just involve the nozzles being blocked or the fluid reservoir empty.
   Cost: Replacing wiper blades is relatively inexpensive, typically costing between £10 and £30.
2. Lights and Indicators
   • Incorrectly adjusted headlights: Headlights that are not aligned properly can result in a minor issue.
   • Fog light or indicator bulb out: A non-functioning bulb, as long as the vehicle has others working, is a minor issue.
   Cost: Replacing a bulb generally costs between £5 and £30, depending on the type of bulb.
3. Bodywork
   • Surface rust or minor damage: Small rust spots or dents that don’t affect the structure of the vehicle are recorded as minor issues.
   • Loose trim or body parts: A piece of trim or a small part that is slightly loose is a minor issue unless it poses a danger.
   Cost: Minor body repairs or rust treatment could cost between £50 and £150 depending on the damage’s extent.
4. Brake Lines and Fluid
   • Slight corrosion of brake lines: If there’s only light corrosion or discoloration but no risk of failure, it may be a minor issue.
   • Low brake fluid levels: This is often marked as an advisory if the levels are just below the recommended minimum.
   Cost: Brake fluid top-ups are relatively inexpensive, usually costing between £10 and £20.
5. Exhaust System (Minor Issues)
   • Small leaks in the exhaust: If the leak doesn’t affect emissions or sound too significantly, it may be classified as a minor issue.
   • Rust or corrosion that hasn’t caused holes: Surface rust or minor corrosion that doesn’t compromise the integrity of the exhaust can be a minor issue.
   Cost: Small exhaust repairs typically cost between £50 and £100.

How MOT Defects Are Recorded

1. Dangerous Defects: These are the most serious failures that make your vehicle unsafe to drive. If the tester finds a dangerous defect, they must notify you, and you will not be able to drive the car away unless repaired immediately.
2. Major Defects: These defects compromise the vehicle’s safety or environmental impact but may not immediately endanger passengers or other road users. The vehicle will fail the MOT and should be repaired before being driven on public roads.
3. Minor Issues: Minor issues do not affect the safety or roadworthiness of the car. These are typically recorded as advisories, meaning the vehicle passes the MOT but will need attention at the next service or MOT.

What to Do if Your Vehicle Fails the MOT

1. Get Repairs Done Immediately: If your car has failed due to a major defect, get it repaired as soon as possible.
2. Book a Re-Test: After the repairs are made, the vehicle will need a re-test to verify the issues have been resolved.
3. Address Minor Issues: Even though minor issues won’t prevent your car from passing the MOT, you should still fix them as they can lead to more serious problems later.

Conclusion

Understanding MOT fail codes is essential for maintaining your vehicle’s safety and roadworthiness.

Major defects are serious and require immediate attention, while minor issues should still be addressed in due course to avoid bigger problems in the future. Knowing the difference between the two helps you prioritize repairs and ensures your vehicle remains safe to drive.

For the best results, always address major defects immediately, and stay on top of minor issues before they become significant problems.

Regular maintenance and understanding MOT guidelines will keep your car in top condition and prevent unnecessary failures.