How to tackle the illegal diesel filter removal ‘industry’ in Belgium and beyond

The TV investigation found that tens of thousands of diesel cars in Belgium were having their diesel particulate filters (DPFs) illegally removed which would result in no controls in the emissions of fine particles. Particles are the main cause of deaths from air pollution and are estimated to be responsible for 400,000 deaths in the EU each year.

The removal of the DPF is illegal but widespread due to the high cost of replacing a faulty filter (around €2,000) or, in some instances, because the driver wants to improve the performance of the engine. The engine management system should detect the filter has been removed but the software is overwritten to ensure no faults are detected. Car manufacturers are unable, or unwilling, to protect the emissions software from being altered – which is of considerable concern given that they are also developing software for driverless cars.

Cars are also required to undergo an annual (or biannual) emissions test in a garage to check the roadworthiness of the car. But on modern vehicles it is common to do this through checking the car software for errors (which fails to show the high emissions). A simple black smoke test will also be performed to measure how dark the exhaust fumes are, but this test is too basic to detect the high emissions in a modern diesel car even if the DPF has been removed.

T&E said four steps need to be taken to fix the current illegal activities:

1. National authorities need to clamp down on the illegal removal of DPFs by catching and fining companies involved in removing the filters. It is easy to find the most blatant advertising for the service, while a simple handheld particle number counter will detect if the DPF has been removed. Spot checks on taxis in the past have in particular identified large numbers of high emission vehicles which have had the DPF removed.
2. National type approval authorities (that approve cars as fit for sale) need to put additional requirements on vehicle manufacturers to ensure the software in cars going onto the road cannot be so easily manipulated. Carmakers could also make more efforts to prevent software being cheated.
3. The European Commission needs to review the Periodic Technical Inspection legislation to tighten up the testing requirements that are completely inadequate and outdated. In particular they should ensure that better tests are introduced which will detect software manipulation and high emissions.
4. City authorities need to make greater efforts to identify grossly polluting cars on the road. New remote sensing equipment can instantaneously measure exhaust emissions from thousands of cars crossing a detection beam and this is now being piloted in London, Paris and Berlin through the TRUE project in which T&E is a partner.

DPFs are not the only part of the engine and exhaust treatment system of a car that is sometimes tampered with. Three-way catalytic converters on petrol cars are sometimes removed and sold particularly just before the car is sold into markets beyond the EU as the catalyst is valuable. Chip tuning a car for higher performance can also hugely raise the emissions. Yet both are hard to detect.

T&E’s clean vehicles director, Greg Archer, said: ‘The illegal removal of diesel particulate filters is an increasingly common practice now. All diesel cars are supposed to be fitted with a DPF. They contribute to the high and harmful levels of particles in the air. It is another example why diesel cars are not clean in the real world. We need actions at EU, national and city level to stop the practice and the car industry needs to make their car software far more difficult to hack!’