The MOT manual doesn't list a DPF warning light as a defect. What it does fail is a particulate filter that has been tampered with, removed or is obviously defective, visible smoke from a car fitted with one, and the engine management light showing a fault.
Testers grade each defect: a major or dangerous defect fails the MOT, a minor one passes but is written on the certificate.
| Defect | Result |
|---|---|
| Evidence that the diesel particulate filter has been tampered with | FailsMajor |
| Defect | Result |
|---|---|
| Exhaust on a vehicle fitted with a diesel particulate filter emits visible smoke of any colour | FailsMajor |
| Engine MIL inoperative or indicating a malfunction | FailsMajor |
From DVSA's MOT inspection manual for cars and passenger vehicles. Contains public sector information licensed under the Open Government Licence v3.0.
In 2025, 1,468 car MOTs failed on the diesel particulate filter: 0.005%, or about 1 in 21,000.
Share of the MOTs that failed on the diesel particulate filter. One MOT can fail for more than one reason.
Share of car MOTs in each mileage band that failed on the diesel particulate filter.
0.00% of MOTs on cars registered in 2005 failed on the diesel particulate filter, against 0.00% for cars registered in 2022.
Models that failed on the diesel particulate filter at least 1.15 times as often as the average car of the same age and mileage, out of 5 with at least 30 MOTs failed on it.
Not the light itself
In 2025, 1,468 car MOTs failed on the diesel particulate filter, about 1 in 21,000.
1 in 21,000car MOTs failed on the diesel particulate filter in 2025
The MOT manual doesn't list a DPF warning light as a defect. What it does fail is a particulate filter that has been tampered with, removed or is obviously defective, visible smoke from a car fitted with one, and the engine management light showing a fault.
In 2025, 1,468 car MOTs failed on the diesel particulate filter: 0.005%, or about 1 in 21,000.
Against the average car of the same age and mileage, the BMW 1 Series (3.2 times as often), BMW 3 Series (2.4 times as often) and Audi A3 (1.9 times as often), going by 2025 MOT results.