Everything you need to know about OBD-II fault codes, MOT tests, and AI-Diagnostics-Pro.
OBD-II is a standardized system that allows devices to interface with a vehicle's computer. It's been mandatory in the UK for petrol cars since 2001 and diesel since 2004.
Typically within 2 feet of the steering wheel, often under the dashboard or centre console.
A Diagnostic Trouble Code (DTC) stored by your car when it detects a problem in the engine or systems.
Plug an OBD-II scanner into your port; it will display a code like P0420. Scanners are available from £8 on Amazon.
Basic fault code information is free. Full AI-powered UK-specific diagnostic reports are £1.59 per report.
Yes, it covers all major manufacturers including Ford, Vauxhall, BMW, Toyota, VW, Mercedes, Tesla and more.
Just your car's year, make, model, engine size and the fault code.
They are intended as indicative UK estimates based on typical parts and labour references, including VAT and average workshop rates. Actual quotes vary by vehicle, region, and garage.
Yes, they reflect average UK workshop rates and local parts pricing — not US or European data.
Yes, it can help interpret EV-related fault codes where those are exposed through the vehicle's diagnostic systems, but coverage varies by manufacturer, model, and scan tool.
Cars before 1996 may use OBD-I which is not standardised. This service is designed for OBD-II vehicles, typically UK petrol cars from 2001, diesel cars from 2004, and many later-1990s vehicles.
Yes, you need an OBD-II scanner to read the code from your car first. These are available from £8 on Amazon.
The MOT is the annual UK safety and emissions inspection for vehicles over 3 years old. Depending on vehicle age and fuel type, an illuminated engine management light can be a Major failure.
A fault code can affect your MOT if it keeps the warning light on, causes emissions issues, or points to a visible defect. Knowing the code in advance gives you time to fix it.
No — the service explains and diagnoses the code. You need a physical OBD-II tool to clear codes from your car's computer.
We do not sell your data. Paid report access expires 12 hours after purchase so you can reopen your purchased report during that period. After that, the underlying session data is scheduled for automatic deletion through storage lifecycle controls, which may complete within roughly 24 hours. Review and feedback submissions are stored in Google Sheets until removed by us.
Yes, full reports are provided in a clear, downloadable PDF format for your records.
Take the report to your mechanic to save time and prevent overcharging. The report gives you a clear understanding of what needs fixing.
No — it is a diagnostic aid to help you understand what your mechanic needs to fix. Always consult a qualified mechanic before carrying out repairs.
If the light is flashing, stop driving immediately and call for assistance. If the light is solid, get it scanned as soon as possible.
Yes, one bad sensor can trigger a chain of multiple error codes. A full diagnostic report will help identify the root cause.
Generic codes (such as many P0xxx faults) use standard OBD-II meanings across manufacturers. Manufacturer-specific codes, including many P1xxx, B1xxx, C1xxx, and U1xxx faults, can vary by make or module and may require specialist knowledge.
These answers are written for UK drivers and summarise general OBD-II, MOT, and repair-cost context. Vehicle age, fuel type, manufacturer implementation, region, and scan-tool capability can all change the exact answer for a specific car.
If your scanner reads beyond engine codes, these are some of the more specific UK guides for body, chassis, and communication faults that often appear with ABS, airbag, BCM, or module-network warnings.
