From the AA
How do they work?
Diesel Particulate filters (DPF) or '
traps' do just that, they catch bits of soot in the exhaust.
As with any filter (think of the bag in your vacuum cleaner) they have to be emptied regularly to maintain performance.
For a DPF this process is called 'regeneration' – the accumulated soot is burnt off at high temperature to leave only a tiny ash residue. Regeneration may be either passive or active.
Passive regeneration
Passive regeneration takes place automatically on motorway-type runs when the exhaust temperature is high. Many cars don't get this sort of use though so manufacturers have to design-in 'active' regeneration where the engine management computer (ECU) takes control of the process.
Active regeneration
When the soot loading in the filter reaches a set limit (about 45%) the ECU can make small adjustments to the fuel injection timing to increase the exhaust temperature and initiate regeneration. If the journey's a bit stop/start the regeneration may not complete and the warning light will illuminate to show that the DPF is partially blocked.
It should be possible to start a complete regeneration and
clear the warning light simply by driving for 10 minutes or so at speeds greater than 40mph.
Im not a mechanic but wondered if you removed the PDF could you use a Hot air gun or blow lamp gently to create the high temp mentioned to clear the soot away. You would need to confirm this with a proper mechanic first.
You say you have only had the car 4 weeks so it can be reasonably assumed that this problem was on the car before you bought it as it has built up enough to light up the dash warning so that would help in the courts.