Is the Engine Management Light an MOT Fail?

When the engine management light fails an MOT

An engine MIL that is “inoperative” (does not work) or that indicates a malfunction is a major defect: section 8.2.1.2 (h) for petrol and 8.2.2.2 (g) for diesel.

The tester turns on the ignition and checks that the engine management light (the manual calls it the engine malfunction indicator lamp, or MIL) comes on and then goes off. On some vehicles the engine has to be started before the light goes off.

Source: GOV.UK: MOT inspection manual, section 8 (nuisance). Last checked 25 October 2026.

Kit cars, amateur built vehicles and American pickups do not have to be fitted with an engine MIL. The light is one item. The tester also does the emissions test for the vehicle’s age: the exhaust gases are measured on petrol engines and the smoke on diesel engines. Hybrids do not have these emissions tests, but their engine light is still checked.

What if the light does not come on at all?

The manual’s check is that the light comes on with the ignition and then goes off. A light that does not work is listed in the same defect as a light that shows a fault, so it is a major defect too.

Older cars

The manual has no engine light check for vehicles first used before these dates, but the emissions checks still apply: the exhaust gases of petrol vehicles first used from 1 August 1975 are measured, and the smoke of diesel vehicles first used from 1 January 1980 is measured with a smoke meter (diesels made before 1980 have a visual smoke check).

Diesel cars

On diesel vehicles, hybrids included, with 4 or more wheels and first used from 1 July 2008, the tester checks the engine light under section 8.2.2.2, the same section as the diesel smoke test. An engine MIL that does not work or indicates a malfunction is a major defect (8.2.2.2 (g)).

What it looks like on the MOT history

The MOT history shows the tester’s defect text with the manual section in brackets. For this fault it uses the manual’s own wording:

• Petrol: “Engine MIL inoperative or indicating a malfunction (8.2.1.2 (h))”
• Diesel: “Engine MIL inoperative or indicating a malfunction (8.2.2.2 (g))”

If the fault was fixed at the test station, our result page lists it under “Failed, fixed at test (PRS)”. Check if your car failed on this before:

There are different MOT rules and processes for vehicles registered in Northern Ireland. Defect details are not provided for Northern Ireland tests. Our Northern Ireland guide explains what an NI MOT check shows.

Other warning lights

The ABS, airbag (SRS), stability control (ESC), tyre pressure, electronic power steering and electronic parking brake warning lights are separate items in the manual, each with its own rule. See them in our MOT self-check.

Before your MOT

• Do the simple checks in our pre-MOT checklist.
• See every fault that fails in what fails an MOT.
• Failed on the light? Our MOT retest guide explains the retest rules.

Frequently asked questions