The Most Common Causes of MOT Failure in the UK

These are the items that fail the most MOTs — and many can be easily fixed before the test.

DVSA data consistently shows the same categories accounting for the majority of MOT failures. Understanding the most common failure points helps you address them before your test — potentially saving you the cost of a retest and the inconvenience of a fail.

1. Lights and Signalling

Lighting faults are the single most common MOT failure category. A blown bulb, fogged lens, or incorrectly aimed headlight is an immediate fail. Do a full walk-around check before your MOT: headlights, sidelights, brake lights, reversing lights, indicators, hazard lights, fog lights, and number plate light.

2. Tyres

Insufficient tread depth (below 1.6mm), tyre damage (cuts, bulges, cord exposure), incorrect tyre size, or mixing radial and cross-ply tyres all cause failures. Always check tread depth before your MOT — inside edge wear is easily missed until an examiner puts a gauge in.

3. Brakes

Worn pads and discs, a seized caliper causing imbalanced braking, or insufficient brake fluid cause brake failures. The MOT includes a roller brake tester that measures the braking force at each wheel — imbalances that you might not notice when driving become apparent on this equipment.

4. Suspension and Steering

Worn ball joints, tie rod ends, wheel bearings, and shock absorbers are all checked. Many fail with no obvious symptom to the driver — they're only detected when an examiner grabs the wheel and checks for play. A pre-MOT suspension inspection can identify these items.

5. Emissions

Diesel vehicles are checked for visible smoke and particulate emissions. Petrol vehicles are tested for CO and HC emissions. A poorly tuned engine, failing catalytic converter, or DPF issue can cause an emissions failure.

Booking a pre-MOT check with PKA Automotive identifies these common failure points before you go in for the test. We fix what's needed and send you in prepared.