How to Pass Your MOT First Time UK — 2026 Checklist

Updated April 2026 · By AI-Diagnostics-Pro AI · 7 min read

Nearly 1 in 3 UK cars fail their MOT — but most failures are preventable. The majority of faults that cause an MOT failure are things you can spot and fix yourself before the test, often for just a few pounds. This checklist walks you through everything to check, with particular attention to OBD2 fault codes, which cause automatic failure.

When Can I Book My MOT?

You can book your MOT up to one calendar month before the due date without affecting your anniversary date. This is useful if you want to get it done early and have time to fix anything that comes up. Your MOT due date is shown on your MOT certificate and can be checked free at gov.uk/check-mot-status.

The Pre-MOT Checklist

1. OBD2 Fault Codes — Check First

An illuminated check engine light is an automatic MOT failure. Before anything else, use an OBD2 scanner (from £15 on Amazon) or AI-Diagnostics-Pro to check for stored fault codes. Even if your check engine light isn't showing, there can be pending codes that will trigger the light during the MOT test. Common codes that cause MOT failure include P0420 (catalytic converter efficiency), P0171 (running lean), and any misfire code.

2. Lights

Lighting faults are the most common reason for MOT failure. Check all of these before your test:

• Headlights — both dipped and full beam
• Sidelights and daytime running lights
• Brake lights — ask someone to watch while you press the pedal, or reverse close to a wall
• Indicators — front, rear and side repeaters
• Hazard lights
• Reversing light
• Fog lights (front if fitted, rear)
• Number plate light

Bulbs are cheap — most are under £5 at any car accessory shop and take minutes to replace. Don't let a £3 bulb fail your MOT.

3. Tyres

Tyre issues cause around 22% of all MOT failures in the UK. Check all four tyres for:

• Tread depth: Legal minimum is 1.6mm across the central three-quarters of the tyre. Use the 20p test — insert a 20p coin into the tread groove. If the outer band of the coin is visible, the tyre is at or below the legal limit.
• Sidewall damage: Any bulges, cuts or cracks are an automatic failure
• Uneven wear: Suggests tracking or suspension issues
• Tyre pressure: Not a direct failure reason but affects tread wear measurement

4. Brakes

Brake problems account for 14% of UK MOT failures. You can check the basics yourself:

• Press the brake pedal firmly — it should feel solid and stop within its travel, not spongy or going to the floor
• Listen for squealing or grinding when braking — indicates worn pads or discs
• Check the brake fluid level in the reservoir under the bonnet — low fluid indicates worn pads or a leak
• Handbrake should hold the car on a slope

5. Windscreen and Wipers

A chip or crack in the driver's zone A (a 290mm band directly in front of the driver) that is larger than 10mm will fail the MOT. Outside of zone A, chips up to 40mm are acceptable. Check your windscreen carefully in bright light.

Wipers must clear the windscreen effectively without smearing. Replacement wiper blades are £8–£20 and fit in minutes.

6. Horn

The horn must work and be audible. Test it — this is one of the easiest checks and an easy fix if it's not working.

7. Exhaust

The exhaust must be securely mounted, not blowing, and your car must pass the emissions test. A visible plume of blue or black smoke from the exhaust is likely to cause a failure. A loose exhaust is rattling money — get it fixed before the test.

8. Body and Structure

The tester checks for excessive corrosion on structural parts including the chassis, floor, sill panels and suspension mountings. Surface rust is usually fine; structural rust that has perforated load-bearing components will fail.

9. Seats and Seatbelts

All seatbelts must retract smoothly, lock when pulled sharply, and the buckles must click and release correctly. The driver's seat must be securely fixed to the floor.

10. Dashboard Warning Lights

Any red warning light or any engine management light that stays on during the test is an automatic failure. Check all warning lights are off before your MOT. If any light is on, diagnose it first.