OBD2 & Car Diagnostics Blog

Expert guides for UK drivers — fault codes, check engine lights, MOT advice and more.

Published 1 Jun 2026

Will an Engine Management Light Fail MOT in the UK?

Will an engine management light fail MOT in the UK? What counts as a fail, what to check before the test, and when it is safe to drive.

Published 1 Jun 2026

Will P0171 Fail MOT in the UK?

Will P0171 fail MOT in the UK? Lean mixture faults, warning-light risk, emissions impact, and what to fix before you book the test.

Published 1 Jun 2026

P0171 Symptoms UK — Lean Mixture Signs and Repair Costs

P0171 symptoms UK guide. Signs of a lean running engine, MOT implications, and typical repair costs before you replace the wrong part.

Published 1 Jun 2026

P0299 Limp Mode UK — What Turbo Underboost Means

P0299 limp mode UK guide. Why turbo underboost sends the car into limp mode, what is usually safe to drive, and what to check before replacing the turbo.

Published 1 Jun 2026

P0299 Repair Cost UK — Turbo Underboost Guide

P0299 repair cost UK guide. Typical turbo underboost causes, what garages usually miss, and realistic repair costs before you approve a quote.

Published 1 Jun 2026

P0300 Repair Cost UK — Random Misfire Guide

P0300 repair cost UK guide. What a random misfire usually means, how urgent it is, and the typical UK repair costs before you authorise work.

Published 1 Jun 2026

P0420 Repair Cost UK — What Drivers Usually End Up Paying

P0420 repair cost UK guide. Realistic cost ranges, the cheapest likely fixes first, and when a catalytic converter quote is probably justified.

Published 1 Jun 2026

P0420 Symptoms UK — What a Catalyst Efficiency Fault Feels Like

P0420 symptoms UK guide. What a catalyst efficiency fault usually feels like, when the car still drives normally, and what to check before replacing the cat.

Published 5 Jun 2026

P0420 Vauxhall Astra UK — Causes, Costs & Fix Guide 2026

P0420 on a Vauxhall Astra? UK guide covering common causes, checks worth doing first, and realistic repair costs for 1.4, 1.6, and 1.8 petrol models.

Updated May 2026

What Is OBD2? Complete Guide for UK Drivers

What is OBD2 and how does it work? Complete UK guide to On-Board Diagnostics — fault codes, scanners, MOT implications and how to use it to save money on repairs.

Updated May 2026

UK MOT Failure Rates by OBD2 Fault Code 2026 — Which Codes Fail Most

Which OBD2 fault codes cause the most UK MOT failures in 2026? Data-driven guide covering P0420, P0171, P0300 and more — with UK repair costs and fix advice.

Updated May 2026

Catalytic Converter Replacement Cost UK 2026 — What to Expect

How much does a catalytic converter replacement cost in the UK in 2026? Prices by car make, DIY vs garage costs, and how to avoid being overcharged.

Updated May 2026

How to Fix P0420 Yourself UK — DIY Guide to Catalyst Efficiency Fault

Step-by-step DIY guide to fixing fault code P0420 in the UK. Check oxygen sensors, exhaust leaks and catalytic converter efficiency before paying a garage £400+.

Updated April 2026

Best OBD2 Scanner UK 2026 — For Every Budget

The best OBD2 scanners for UK drivers in 2026. From budget dongles to professional tools, reviewed and ranked with UK-specific advice.

Updated April 2026

Check Engine Light On But Car Drives Fine UK — Should You Worry?

Check engine light on but your car feels normal? Here's what it likely means for UK drivers, which codes to watch out for, and what to do before your MOT.

Updated April 2026

Flashing Check Engine Light UK — What It Means & What to Do

Your check engine light is flashing — here's exactly what it means, whether it's safe to drive, and what to do next. UK-specific advice.

Updated April 2026

How to Pass Your MOT First Time UK — 2026 Checklist

Nearly 1 in 3 UK cars fail their MOT. Use this 2026 checklist to spot common failures before your test and pass first time — including OBD2 checks.

Updated April 2026

How to Read OBD2 Codes Without a Scanner UK — Cheap Alternatives

Don't have an OBD2 scanner? Here are the cheapest ways to read your car's fault codes in the UK, including free apps, cheap dongles and AI diagnosis.