Decode your car’s fault. Check any MOT. Fix it yourself.
Free UK fault code library, MOT pass rates for 1208 models built from 33.1 million official DVSA tests, and plain-English advisory explanations.
1769fault codes explained
1208models with MOT stats
77.5%UK pass rate 2025
188advisories decoded
Engine light on? Look up the code
All fault codes →Plug in any OBD2 reader, note the code, and get causes, DIY diagnosis steps and realistic UK repair costs.
P0011'A' Camshaft Position - Timing Over-Advanced or System...
P0016Crankshaft Position - Camshaft Position Correlation
P0087Fuel Rail/System Pressure - Too Low
P0088Fuel Rail/System Pressure - Too High
P0101Mass or Volume Air Flow Circuit Range/Performance
P0102Mass or Volume Air Flow Circuit Low Input
P0113Intake Air Temperature Sensor 1 Circuit High
P0128Coolant Thermostat (Coolant Temperature Below Thermostat...
MOT pass rates by model
All makes & models →First-test pass rates from the 2025 DVSA dataset — see what fails before you buy or book.
| Model | Tests | Pass rate | vs UK avg (77.5%) |
|---|---|---|---|
| Ford Fiesta | 1,279,795 | 71.7% | |
| Ford Focus | 850,793 | 74.3% | |
| Volkswagen Golf | 782,869 | 77.8% | |
| Vauxhall Corsa | 760,175 | 68.8% | |
| Volkswagen Polo | 577,151 | 71.4% | |
| Vauxhall Astra | 571,373 | 72.1% | |
| Nissan Qashqai | 537,795 | 71.4% | |
| Toyota Yaris | 406,942 | 77.8% | |
| Audi A3 | 369,274 | 78.5% | |
| BMW 3 Series | 346,191 | 77.7% |
What UK cars fail on
Advisories explained →1. Suspension4,606,007 defects recorded in 2025
2. Lamps, reflectors and electrical equipment4,121,968 defects recorded in 2025
3. Brakes3,595,998 defects recorded in 2025
4. Tyres2,786,889 defects recorded in 2025
5. Body, chassis, structure1,411,336 defects recorded in 2025
6. Visibility1,298,684 defects recorded in 2025
7. Noise, emissions and leaks1,250,830 defects recorded in 2025
8. Steering813,273 defects recorded in 2025
Guides
All guides →
Engine management light on? What to do (and what it costs)Steady vs flashing, MOT rules, and the 10-minute DIY diagnosis.
Which OBD2 scanner should you buy? (UK, 2026)Code reader vs full-system scanner vs Bluetooth dongle — honest advice.
Car battery health check: test it yourself in 5 minutesVoltage chart, load test basics, and the signs a battery is dying.
MOT advisories explained: ignore, monitor or fix?What advisories really mean, whether to fix them, and buying a car with them.
MOT cost in 2026: the £54.85 cap and what you’ll actually payMaximum fees, typical prices, retest rules and how to avoid a fail.
Pre-MOT checklist: 15 minutes that prevent most failuresThe DIY walk-round that catches bulbs, tyres, wipers and warning lights.
Engine management light flashing and car juddering: stop or drive?A flashing EML plus shaking usually means an active misfire — treat it differently from a steady light.
Car turns over but won’t start: fuel, spark or signal?Cranking is not the same as clicking — this fault tree starts after the starter is already turning.
DPF light won’t go off after a long drive? Don’t repeat the same runIf one correct regeneration drive did not clear it, find out what is preventing regeneration.
Car cuts out when slowing down or at junctions: what to testAn intermittent stall is often hidden in pending codes and live data even when the garage cannot reproduce it.
Car overheating but coolant is full: five causes to checkA full expansion tank does not prove coolant is circulating or the temperature reading is correct.
Coolant keeps disappearing but there’s no leak: where it goesHot-only leaks, the heater matrix, cap loss and internal leaks can leave no driveway puddle.