You've bought a car and something's wrong. But is it a "fault" in the legal sense? Can you actually reject it? Here's how to tell.
The Legal Test
Under the Consumer Rights Act 2015, you can reject a car if it fails one of three tests:
- Not of satisfactory quality – It has defects a reasonable person wouldn't expect
- Not fit for purpose – It can't be used as a car should be used
- Not as described – It doesn't match what you were told
A "fault" is anything that causes the car to fail one of these tests.
Clear-Cut Faults
These are almost always grounds for rejection:
Mechanical Failures
An engine that won't start or runs poorly, a gearbox that grinds, slips, or fails, a clutch that judders or won't engage, brakes that don't work properly, steering that pulls, feels heavy, or makes noise, suspension failures, and cooling system leaks or overheating are all clear-cut mechanical faults.
Electrical Problems
Electrical faults include a battery not holding charge (beyond normal age), central locking failures, windows not working, dashboard warning lights that won't clear, infotainment system failures, and sensor malfunctions.
Safety Issues
Airbag warning lights, ABS or traction control failures, seatbelt problems, structural issues, and brake failures are always grounds for rejection regardless of the car's age or price.
Undisclosed Issues
Accident damage not revealed, outstanding finance, clocked mileage, previous write-off status (Cat S/N), and hidden rust or water ingress are all grounds for rejection because the car isn't as described.
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Grey Area "Faults"
These depend on context:
Wear Items
Brakes, tyres, and clutches wear out. Whether wear constitutes a fault depends on whether the wear was disclosed before purchase, whether it's appropriate for the car's mileage, and whether the component failed prematurely. A clutch that fails at 20,000 miles is likely faulty. One that's worn at 80,000 miles is probably just wear.
Cosmetic Issues
Scratches, dents, and interior wear are usually acceptable on used cars provided they match the car's age and price, they were visible when you viewed the car, and they weren't deliberately concealed. A scratch on a £3,000 car is different from one on a £30,000 car.
Age-Related Issues
Older cars have more problems. But age doesn't excuse fundamental mechanical failures, safety issues, problems that weren't disclosed, or rapid deterioration shortly after sale.
Intermittent Problems
Faults that come and go can be tricky, but they're still faults if they affect the car's quality. Document every occurrence with dates, times, and mileage. Video evidence is particularly powerful for intermittent problems, and diagnostic codes often capture issues even when they're not actively showing symptoms.
What's NOT Usually a Fault
Normal Characteristics
Diesel clatter, turbo whistle, firm sports suspension, and features that work exactly as designed (even if you don't like them) are all normal characteristics of a vehicle rather than faults.
User Preference
Fuel consumption that matches manufacturer figures, road noise typical for the model, handling characteristics normal for the car type, and features you simply didn't check before buying are matters of personal preference, not defects.
Post-Sale Damage
Issues caused by your own driving, accident damage after purchase, problems resulting from neglected maintenance, and faults caused by modifications you've made are your responsibility, not the dealer's.
Disclosed Issues
Problems the dealer told you about before purchase, faults that were reflected in a lower price, and issues you explicitly agreed to accept cannot usually be the basis for a rejection claim.
The Timing Question
When did the fault exist?
Within 30 Days
Any fault present at delivery = right to reject. Learn more about the 30-day rejection timeline. You don't need to prove when it developed. If it's there within 30 days, it's presumed to have been there at sale.
Within 6 Months
Faults are presumed to have existed at sale unless the dealer can prove otherwise. The burden of proof is on them.
After 6 Months
You need to prove the fault existed at sale. Usually requires an independent inspection showing the problem pre-dated your purchase.
How to Prove a Fault
Documentation
Take photos and videos of the problem as it occurs, capture images of any dashboard warning lights, and record the mileage, date, and time at each occurrence. The more you document, the stronger your case becomes.
Diagnostic Evidence
OBD fault codes, dealer diagnostic reports, independent garage assessments, and error logs stored in the car's computer all provide objective proof of a fault that's difficult for a dealer to dismiss.
Expert Evidence
An independent inspection report carries significant weight, along with a mechanic's written opinion, technical assessments from specialists, and manufacturer technical bulletins that acknowledge known issues.
Pattern Evidence
Online forums showing common problems with your model, recall notices, technical service bulletins, and similar complaints reported to Trading Standards can all demonstrate that your issue is a recognised defect rather than an isolated incident.
Real Examples
✅ IS a Fault
Problem: Engine management light comes on after 2 weeks, diagnostic shows injector fault. Why: Mechanical failure affecting performance, present within 30 days.
✅ IS a Fault
Problem: Car described as "full service history" but missing 3 years of stamps. Why: Not as described – the description was false.
✅ IS a Fault
Problem: 4-year-old BMW gearbox fails at 45,000 miles. Why: Premature failure – gearboxes should last much longer.
❌ NOT a Fault
Problem: Brakes need replacing at 60,000 miles. Why: Normal wear item at typical interval.
❌ NOT a Fault
Problem: Diesel engine is noisy. Why: Characteristic of diesel engines, not a defect.
⚠️ DEPENDS
Problem: Air conditioning doesn't blow cold. Why: Fault if not disclosed; acceptable if sold as "AC needs regas" at reduced price.
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What If the Dealer Disagrees?
Dealers often claim "that's not a fault, it's wear and tear," or that all cars of this age have the same problem, or that you should have spotted it before buying. None of these are valid defences. The Consumer Rights Act defines satisfactory quality – the dealer doesn't get to. Age doesn't remove the requirement for basic functionality. And it's the dealer's duty to sell satisfactory goods, not yours to be an expert mechanic.
If they won't accept it's a fault, get an independent inspection, put your rejection in writing, contact your finance company if applicable (they're jointly liable), and escalate to court if necessary.
The Bottom Line
A "fault" is anything that makes the car not of satisfactory quality, not fit for purpose, or not as described. The key questions are whether a reasonable buyer would expect this problem, whether it affects the car's functionality or safety, whether it was disclosed before purchase, and whether it's appropriate for the car's age, mileage, and price. If the answers suggest you've been sold a substandard product, you likely have grounds to reject.
Not sure if your problem counts as a fault? Get a free assessment – we'll tell you where you stand.
