So let’s put this in layman’s terms,
The DPF (Diesel Particulate Filter) is a honeycomb style filter inside a modern exhaust pipe. It has one job and one job alone and that is to catch soot. It does that very well. About 85% and in some situations 100% of the dirty soot particles are caught by the DPF making the gases that come out the back of the car much cleaner than they were 20 years ago.
When the DPF has got to a certain level of “soot blockage”, other systems on the car take over and burn off all the soot in one go so the filter becomes clean again. This is called “regeneration”.
Now for some reason, this regeneration is not happening on your vehicle and the dash is telling you that there is a problem. This can happen for 2 main reasons. Either the vehicle is doing lots of short journeys so the regeneration is constantly being interrupted before it can complete the clean or one of the systems that look after the DPF has failed.
So what do I do?
The first thing is run some tests to see if the DPF is actually blocked or if the car is lying to you. This can happen if a sensor has failed. I will then measure the back pressure before the DPF and this will give me a good idea about what is going on and what needs to be done.
If the DPF does need cleaning I will inject some acid on to the front face of the DPF to dissolve the soot that is choking the filter. Once this is complete, I will run a detergent through the DPF to further clean the filter and neutralise the acid. While this is happening, I will be constantly checking the diagnostic systems and some components in the engine bay to ensure a perfect result. I will then re-measure the DPF back pressure to make sure that the exhaust gasses can flow freely through the filter as they should.
Usually the car will then be road tested to monitor the “regeneration” using live data.