What did DVSA test?
A catalytic converter cleans the exhaust of a petrol car, and a DPF traps soot from a diesel. When one fails, a replacement from an independent parts maker is usually far cheaper than the original part. Replacement parts must still be approved to the same emissions standard as the car.
DVSA's Vehicle Market Surveillance Unit bought replacement parts for three popular small cars and tested them against the UN emissions rules (Regulation No. 103 and Regulation (EC) No. 715/2007).
Which parts failed?
| Car | Part | Maker | Result |
|---|---|---|---|
| Fiat 500 TwinAir 0.9 petrol, Euro 6 | Catalytic converter BM91759H | BM Catalysts (UK) | Failed: hydrocarbons, carbon monoxide |
| Catalytic converter FI6062T | EEC (UK) | Failed: hydrocarbons, carbon monoxide, nitrogen oxides | |
| Catalytic converter 55326 | AS (outside UK) | Failed: hydrocarbons, carbon monoxide, nitrogen oxides | |
| Ford Fiesta 1.5 diesel, Euro 5 | DPF FD5103 | AS (outside UK) | Failed |
| DPF FR6133T | EEC (UK) | 2 of 3 failed: hydrocarbons, carbon monoxide, nitrogen oxides, particle number | |
| DPF BM11244H | BM Catalysts (UK) | Passed | |
| Renault Clio 0.9 petrol, Euro 6 | Catalytic converter BM92271H | BM Catalysts (UK) | 3 of 4 failed: hydrocarbons, carbon monoxide |
| Catalytic converter 28879 | Walker (outside UK) | 2 of 3 failed, including nitrogen oxides | |
| Catalytic converter 30225 | AS (outside UK) | Passed |
Both UK makers told DVSA they had accepted its recommendation to stop making and selling the failing parts in the UK. DVSA reported the two overseas makers to the authorities that approved their parts, and says the type approval authorities will carry out in-service conformity checks.
What should drivers do?
If you own one of these cars and had the catalytic converter or DPF replaced in the last few years, ask the garage which part was fitted. The part number is usually on the invoice. DVSA's report does not say what owners of cars with a failing part fitted should do, and no recall of fitted parts has been announced. We will update this article if that changes.
A converter or DPF that does not clean the exhaust properly can lead to an MOT emissions fail, and on diesels, to a blocked DPF and expensive repairs. A cheap part that fails the MOT is not a saving.
- Ask for a replacement that is type-approved for your exact car and engine, and keep the invoice.
- Check whether your car has failed on emissions before: our free MOT history check lists every test and defect.
- Get ready for the test with our MOT checklist and see what an MOT costs.
Questions drivers ask
Which catalytic converters failed DVSA testing?
Parts for the Fiat 500 TwinAir 0.9 and Renault Clio 0.9, and DPFs for the Ford Fiesta 1.5 diesel, from EEC, BM Catalysts, AS and Walker. Some parts from BM Catalysts and AS passed. DVSA published the results on 21 October 2026.
Are the failing parts still on sale?
No. DVSA says all non-compliant parts have been removed from production and sale, and both UK makers agreed to stop making and selling them in the UK.
Can an aftermarket catalytic converter fail the MOT?
Yes, if it does not clean the exhaust enough, the car can fail the emissions test. Replacement parts must be approved to the same emissions standard as the car.
Sources
Facts checked against the sources above on 23 October 2026. Spotted something out of date? Tell us.
