AI-Diagnostics-Pro · For UK drivers
Check Engine Light On? Get Your Fault Code Report
Enter your OBD-II fault code and vehicle details. Get likely causes, UK repair-cost estimates, MOT risk and step-by-step fix guidance — specific to your exact year, make and model. Ready in about a minute.
Get My AI Report — £1.59 →What your report includes
- ✓What the fault code most likely means on your specific vehicle
- ✓Whether it is safe to drive or whether you should stop immediately
- ✓Indicative UK repair-cost ranges before you call a garage
- ✓MOT risk assessment, repair priorities and sensible next steps
- ✓Step-by-step fix guidance with tool recommendations for DIY repairs
- ✓Supports generic and many manufacturer-specific OBD-II codes
What UK drivers say
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How it works
Enter your fault code
Type in the OBD-II code from your scanner or dashboard warning light.
Add your vehicle details
Year, make, model, engine and mileage so the report is specific to your car.
Get your report
Pay £1.59 and receive a detailed AI-generated report in about a minute.
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MOT history, mileage, valuation and legal status — free, instant.
Top 15 Most Searched OBD2 Codes in the UK
Click any code for symptoms, causes, UK repair costs and MOT advice
Frequently asked questions
What does a check engine light mean?
The check engine light (engine management light) means your car’s ECU has detected a fault and stored a diagnostic trouble code. It does not tell you what is wrong on its own — you need an OBD-II scanner to read the specific fault code. AI-Diagnostics-Pro then interprets that code and gives you a full UK-specific diagnostic report.
Is it safe to drive with a check engine light on?
If the light is flashing, stop driving immediately — a flashing light usually indicates a serious engine misfire that can cause rapid catalytic converter damage. If the light is solid and steady, it is generally safe to drive short distances, but you should scan the code as soon as possible to understand the risk.
How much does a car diagnostic cost at a garage?
Most UK garages charge between £40 and £120 just to plug in their diagnostic machine and read the codes. AI-Diagnostics-Pro gives you a full AI-generated diagnostic report specific to your vehicle for just £1.59 — a fraction of the cost, available instantly without a garage visit.
Do OBD2 fault codes work on all cars?
They work on OBD-II compatible cars. In the UK that generally means petrol cars from 2001 and diesel cars from 2004 onwards, plus many late-1990s vehicles. Once a car is OBD-II compatible, the standard format is shared across manufacturers, but some fault codes are still manufacturer-specific.
Can I clear a fault code myself?
You can clear a fault code using an OBD-II scanner, but if the underlying fault has not been fixed, the code will return within a few drive cycles. Clearing codes before an MOT test without fixing the fault is not recommended — the code will reappear and the MIL will illuminate, failing the test. Always fix the fault first.
What is the most common OBD2 fault code in the UK?
P0420 (Catalyst System Efficiency Below Threshold) is one of the most common fault codes seen in UK garages. It indicates the catalytic converter is not operating efficiently. Before replacing the catalytic converter (which can cost £400–£800), it is worth checking the oxygen sensors first — a faulty O2 sensor is a cheaper fix that often triggers the same code.
What is an OBD2 fault code?
When your car’s check engine light comes on, it means the ECU (Engine Control Unit) has detected a problem and stored a fault code — also called a DTC (Diagnostic Trouble Code). OBD-II fault codes use a standardised format across all major manufacturers, but some codes are generic while others are manufacturer-specific. In the UK, OBD-II is standard on petrol cars from 2001 and diesel cars from 2004, with many late-1990s vehicles also supporting it.
Will my fault code fail the MOT?
For vehicles where DVSA MIL checks apply, an illuminated check engine light (malfunction indicator lamp) is a Major MOT failure. The exact rule depends on the vehicle’s age and fuel type, so an active fault code should always be checked before test day.
Why do UK-specific repair costs matter?
Most online OBD2 resources show US dollar repair costs, which bear no relation to what UK garages charge. UK labour rates, parts prices and MOT requirements are completely different from the US and even from mainland Europe. AI-Diagnostics-Pro provides indicative UK repair-cost ranges using typical parts and labour references, including VAT.
Supports 30+ manufacturers including Ford, Vauxhall, BMW, Audi, Volkswagen, Mercedes-Benz, Toyota, Nissan, Kia, Hyundai and many more.