An active check engine light is an automatic MOT failure in the UK. Here's what you need to know about fault codes and your MOT test.
Under current DVSA (Driver and Vehicle Standards Agency) testing standards, an illuminated malfunction indicator lamp (MIL) — commonly called the check engine light or engine management light — is an automatic MOT failure. This applies regardless of whether the vehicle drives normally or whether the underlying fault is minor.
The MOT tester checks for the MIL by connecting an OBD-II scanner to your vehicle's diagnostic port. If any fault codes are present and the check engine light is on, the vehicle will receive a Major fault and fail the test.
1. Scan your car for fault codes at least 2 weeks before your MOT — this gives you time to fix any issues
2. Get a full AI diagnostic report from AI-Diagnostics-Pro to understand the fault, cost to fix and MOT risk
3. Have any active faults repaired and the codes cleared before booking your MOT appointment
4. After repair, drive the car for at least 20–30 miles to complete the OBD readiness monitors before the test