Removing the DPF is a popular method of solving problems with DPFs and FAPs. A clogged DPF leads to the loss of power and constant car failures. The particulate filter light and possibly engine failure light are always on. Replacing a DPF at the manufacturer’s service station is very expensive, so many drivers choose to deactivate the filter and physically remove it. Is this the only way, though? 

The least invasive method, one you should check out first, is forced DPF burning out. Such forced cleaning takes place when the car is parked, and a diagnostic tool is activated. Naturally, only advanced diagnostic equipment and services (including the authorised ones) have such a possibility. Burning out the DPF takes approximately several minutes.

After the diagnostician gives the command, the engine driver revs up, which leads to the ignition of the soot collected in the filter, and next calculates the filling after the burning out. If you drive mostly short distances, with frequent stopping and starting of the car, there is no possibility of the particulate filter self-regeneration (burnout), and it can get clogged. However, it does not mean that the filter is broken. It gathers two types of substances – the soot that is carbon-related or carbon itself, and these are burned out during the process, and the ash that is the result of burning up and is impossible be burnt out completely.

The engine control unit, using the data on the mileage, on the fuel consumption, and on the style of driving, constantly calculates the amount of filter saturation with ash and soot. It attempts to burn out the soot (as I already mentioned, you can also induce the burning out), and the ash is accumulated to the capacity limit of the filter. If the DPF light is on but your car does not have high mileage, more often than not goes only short distances, and your driving style is rather moderate, then forced burnout may solve the problem.

When “unclogging” the DPF or the FAP by forced burnout is not possible, after removing it from the car, you can try clearing the particulate filter using chemical, mechanical or hydrodynamic methods. It boils down to dissolving or mechanical breaking down (by vibrations or ultrasounds) of carbon deposits, soot and ash, collected in the filter and removing them from the filter. Unless it has some mechanical damage (it is melted or crushed), the filter recovers most of its efficiency.

Since the ash content in the filter is estimated not only on the basis of the data from the differential pressure sensor (as it is designed specifically to assess the content of the soot) but is based mostly on the amount of fuel used, you must “inform” the engine controller that the filter has been emptied of ash. As the particulate filters manufacturers do not provide for mechanical cleaning, and usually put much effort in preventing easy removal of the filter, the only solution seems to be so-called DPF exchange programming. The controller takes the regenerated DPF as a new one and begins filling it with the ash from scratch.