Why should the DPF be cleaned?
The vehicle will clean the DPF filter by using a process called passive regeneration, This starts when the vehicle is driven over 40mph for a period of minutes at a time. The vehicles will heat the exhaust gasses to very high temperatures of around 500 degrees celcius which will turn this soot into harmless ash.
The problem is that many drivers live in towns or cities and the short quick driving conditions do not allow for the regeneration process to be completed. The vehicle will automatically try to correct this issue and clean the DPF by using a process called active regeneration, however this process is not always successful which leads to excessive soot eventually blocking the DPF filter which requires urgent mechanical assistance.