The MOT test is an annual vehicle safety inspection required for most cars in the UK once they turn 3 years old. Around 30% of vehicles fail their MOT on the first attempt, so understanding the most common MOT failure reasons can help drivers prevent issues and ensure their car passes.
What Can Fail an MOT?
There are many safety-critical automotive defects that can cause a car to fail its MOT. Being aware of these roadworthiness problems and addressing them proactively is key to MOT’s success. Here are some of the top causes of test failures:
Lighting and Signaling Issues
Faulty headlights, brake lights, indicators, or other exterior lights are the main reasons for MOT failures. Typical problems include:
- Blown bulbs
- Damaged lenses
- Misaligned aim
Performing regular at-home inspections and replacing faulty lights is an easy way to avoid this major MOT failure reason.
Suspension Problems
Worn-out suspension components like shock absorbers, springs, linkages, and bushings often lead to MOT test failures. This causes unstable handling, uneven tire wear, and safety issues. Inspecting your car’s suspension system and making necessary repairs prevents problems.
Brake System Defects
Defective brakes are an automatic MOT failure and a serious safety concern. Typical issues are:
- Worn brake pads
- Warped discs
- Leaking hoses
- Low fluid levels
Replacing brake parts as required and flushing fluid yearly maintains proper brake function and roadworthiness.
Also read: Understanding MOT Results
Tyre Condition and Tread Depth
Bald tires or those with insufficient tread depth (under 1.6mm) almost always fail the MOT. Other common tyre-related reasons include:
- Uneven wear
- Sidewall damage
Monitoring tread depth, rotating tyres routinely, and maintaining proper inflation help avoid failures.
Exhaust and Emission Control Issues
Leaking exhaust pipes, corroded components, faulty oxygen sensors, or defective catalytic converters lead to MOT exhaust emission test failures. Regular inspections and emission control servicing are essential.
Steering System Faults
Excessive play or looseness in steering components, like linkages due to wear, will fail the MOT. Power steering fluid leaks are another common issue. Proper lubrication and repairs of steering parts are required.
Body and Undercarriage Corrosion
Extensive rust or corrosion, especially on load-bearing structures like subframes, can cause MOT failure. Treating rust early and repairing corroded sections helps avoid problems.
Registration Plates and Lights
Having incorrect registration plate sizes and colours or being unreadable will automatically fail. Missing, damaged, or obscured plate lights also frequently factor into MOT failures. Installing proper UK spec plates and working lights avoids these easily preventable issues.
How to Minimize MOT Failure Risks?
The most common MOT test failure reasons boil down to neglected vehicle maintenance and lack of preventative care. By properly maintaining your car’s critical safety systems and knowing what to look out for, you can greatly reduce risks:
Key Preventative Measures
| Area | Maintenance Tips |
| Lights | Inspect all lights and bulbs regularly |
| Suspension | Check components yearly |
| Brakes | Replace parts as required |
| Tyres | Monitor condition and tread depth |
| Emissions | Service control system yearly |
| Steering | Lubricate and inspect linkage |
| Body | Treat rust and corrosion early |
Pre-MOT Inspections
| Inspection Item | Details |
| Lights & Signals | Test all vehicle lights |
| Tyres | Check inflation and tread depth |
| Brakes | Assess pad thickness |
| Fluids | Look for any leaks or drips |
| General | Inspect for loose parts or fittings |
| Body | Scan for corrosion |
Being proactive about minor issues before they become major repair problems is the best way to pass your annual MOT test the first time and keep vehicles roadworthy. Paying attention to the most common MOT failure reasons also ensures you never wonder, “what can fail an MOT?” again either. Maintaining your automobile diligently year-round makes all the difference.
