Car symptom checker · free · no signup
What's Wrong With My Car?
You don't need a fault code to start. Pick what the car is doing, answer a few quick questions, and see the most likely causes, ranked — with a clear verdict on whether it's safe to keep driving. Add the registration and we'll check the answer against that car's own record.
Free interactive diagnosis
What is your car doing?
Browse by symptom
Every cause for each symptom, ranked, with whether it's safe to keep driving.
Engine management light
Engine management light on: causes and is it safe to drive?
Other warning lights
Dashboard warning light on? What it means and what to do
Won't start
Car won't start? Find the likely cause
Exhaust smoke
Smoke from the exhaust: what white, blue and black smoke mean
Running poorly
Car running badly? Losing power, misfiring, stalling or juddering
Leaks
Car leaking fluid? Identify it by colour, smell and position
Brakes
Brake problems: squeaking, grinding, judder or a soft pedal
Steering & vibration
Steering problems: pulling, shaking, heavy or vague steering
Noises
Strange noise from your car? Find what's making it
How it works
Pick the symptom
Won't start, a warning light, smoke, poor running, a leak, the brakes, the steering or a noise.
Answer a couple of questions
Each one is chosen to split the possibilities apart — the same questions a mechanic asks at the counter.
Add the reg, if you like
We check the shortlist against the car's MOT advisories, mileage, age, engine and how its model tends to fail — all free government data.
What the car's record adds
Its latest MOT. If a tester flagged the part behind your symptom — a worn anti-roll bar link for a knock over bumps, say — it moves up the list and we quote the advisory with its date. If it was flagged once and gone by the next test, we assume it was fixed and don't count it.
Its age, mileage and use. A diesel covering 5,000 miles a year is far more likely to have a blocked DPF than one doing 20,000. A ten-year-old car on its original battery is a different starting point from a new one.
Its engine. We know whether it has a timing belt or a chain, and whether the belt interval has come round — which matters for anything that could be the timing drive. Where the manufacturer has acknowledged a problem with that engine, we say so and show the source.
Its model. From our analysis of millions of DVSA MOT results, we know which areas this model fails on more than other cars its age — see the common faults checker.
What it can't see is whether work was done between MOTs. That's what the manufacturer's service history shows.
Common questions
How accurate is the symptom checker?
It gives the shortlist a mechanic would give you over the counter, ranked by how often each cause is behind that symptom. It narrows the problem down and helps you avoid being blinded with science at a garage, but it can't inspect the car. Anything involving brakes, steering or suspension should be checked in person before you rely on it.
What does adding my registration change?
With a registration we look up the car's own free government records: its MOT advisories and failures, the mileage trail, its age and engine, and how often that model fails its MOT in each area. A worn part a tester flagged at the latest MOT, for example, moves up the list and is quoted back to you. Advisories that disappeared at the next MOT are treated as probably fixed and aren't counted.
What do the green, amber and red verdicts mean?
Green means it's usually a nuisance rather than a danger — get it checked when convenient, and sooner if it gets worse. Amber means you can drive gently but should get it looked at within days. Red means stop: don't drive it until it's been checked, because carrying on risks the engine, the brakes or the steering, and recovery costs less than the damage. For a car that won't start, the verdict tells you whether to work through the simple checks first or stop trying and have it recovered.
Is this a diagnosis? Can I rely on the verdict?
No. It's general information to help you understand a problem, not a diagnosis, an inspection or professional advice. We haven't seen the car, and the real cause may not be on the list. Have the car checked by a qualified mechanic before relying on it and follow their advice over ours — and if you're unsure whether it's safe, don't drive it. You use the tool at your own risk, and we can't accept responsibility for decisions made on the strength of it.
Does it tell me if my car has a known engine problem?
Only where the manufacturer itself has acknowledged the problem — through a recall, an extended warranty or an official service action — and we show the source. We don't repeat press or forum reports about named engines as fact.
Why does it ask whether my car is petrol or diesel?
Because the likely causes are completely different. A diesel that won't start on cold mornings is usually glow plugs; a petrol one is usually fuel or ignition. If you add the registration we already know, so the question is skipped.
Should I still get the fault codes read?
Yes, if there's a warning light. A fault code narrows the list further than any question can, and most garages or a cheap OBD code reader will read it.
Does it cost anything?
No. The checker is free with or without a registration and uses only free government data. The paid product on this site is a different thing: the manufacturer's own dealer service records for a car, which show what was actually replaced and when.