This guide uses UK garage pricing data from AA, RAC and independent garage surveys, reviewed quarterly. Use the links below for official references.
When your check engine light comes on, one of the first questions is: how much will it cost to find out what's wrong?
UK garages charge anywhere from £40 to £150 just to plug in a diagnostic scanner and read your fault codes. But there are cheaper alternatives that can save you money — and help you avoid unnecessary garage visits.
| Type of Garage | Typical Cost | What You Get |
|---|---|---|
| Independent garage | £40 – £80 | Basic fault-code scan and interpretation |
| Fast-fit chain (Kwik Fit, Halfords) | £50 – £100 | Diagnostic scan with basic advice |
| Main dealer | £100 – £150 | Manufacturer-specific diagnostics with deeper system access |
| Mobile mechanic | £50 – £90 | Diagnostic scan at your location |
A typical garage diagnostic session includes:
Before paying £40-150 for a garage diagnostic, consider these options:
Basic OBD2 scanners are available from £8 on Amazon. They'll read the fault code, but won't tell you what it means or what to fix.
Bluetooth OBD2 adapters work with free apps like Torque (Android) or OBD Fusion (iOS). Same limitation as basic scanners — you get the code but not the diagnosis.
An AI-powered diagnostic report like AI-Diagnostics-Pro gives you a detailed analysis specific to your vehicle — including likely causes, UK repair costs, MOT risk, and step-by-step fix guidance.
Vehicle-specific analysis with UK repair costs, MOT risk, and step-by-step fix guidance — 97% cheaper than a garage diagnostic.
Get My Report — £1.59 →While DIY options work for simple issues, there are times when a garage diagnostic is worth the money:
| Scenario | Garage Cost | DIY Cost | Saving |
|---|---|---|---|
| P0420 catalyst efficiency | £60 – £120 | £8 scanner + £1.59 report | Up to £110 |
| P0171 system too lean | £50 – £100 | £8 scanner + £1.59 report | Up to £90 |
| P0300 random misfire | £50 – £100 | £8 scanner + £1.59 report | Up to £90 |
| P0299 turbo underboost | £60 – £120 | £8 scanner + £1.59 report | Up to £110 |
| Multiple codes (3+) | £80 – £150 | £8 scanner + £1.59 report | Up to £140 |
Most UK garages charge between £40 and £120 to plug in a diagnostic scanner and read fault codes. Main dealers typically charge £100-150. Some garages waive the fee if you proceed with the repair.
Yes, you can read fault codes yourself using a cheap OBD2 scanner from £8 on Amazon, or a free smartphone app with a Bluetooth adapter. However, understanding what the codes mean still requires knowledge or a diagnostic report.
It depends on complexity. For simple codes like P0457 (loose fuel cap), you can fix it yourself. For complex issues involving multiple systems, a garage's expertise can save you from replacing the wrong parts.
Main dealers typically charge between £100 and £150 for a diagnostic session. They use manufacturer-specific tools that can access deeper systems, but independent garages often provide the same basic diagnostic for £40-80.
The cheapest way is to buy a basic OBD2 scanner from £8 on Amazon or use a free smartphone app with a Bluetooth adapter. For a detailed analysis, an AI diagnostic report like AI-Diagnostics-Pro costs just £1.59.
Sources: AA Car Diagnostics · RAC Car Maintenance · Which? Car Maintenance
AI-Diagnostics-Pro provides AI-generated information for educational purposes only. Garage prices are approximate and may vary by location and vehicle. Always get multiple quotes before authorising work. Content reviewed July 2026.