Car Diagnosis Guides

Use these guides to understand what your car's fault codes mean and how to diagnose problems before calling a mechanic — or to understand what a mechanic has told you.

• Engine Diagnostic — How We Find What Is Wrong With Your Engine

  How a professional engine diagnostic works — from OBD2 scan to live data, compression test and physical checks. Mobile mechanic Reading and Berkshire. From £45.

• OBD2 Fault Codes Explained — How to Read and Understand Them

  What are OBD2 fault codes? How to read them, what P, B, C and U codes mean, common codes and why a professional scanner reads more than a cheap Bluetooth reader.