The DPF filters, harmful particulates (soot) from the exhaust gas and has been designed to regenerate (clean) itself automatically, however it can only do this by heating the DPF to high temperature, the ECU injects additional fuel on the exhaust stoke to increase exhaust gas temperatures to raise DPF temperature(600ºC) to ignite and clean the soot away, however it can only do this at high RPM (above 2.000rpm) so if it comes on, you need to drive at high speed for 20-30minutes to clean the DPF.
If the DPF light is the only warning light on, you should drive vehicle at over 2000 rpm (to raise exhaust temperature) for 20 minutes without delay, this should regenerate the particulate filter (burn off the accumulated soot) and the light should go out.
If you have DPF light and the engine management light are on together, have vehicle towed to dealer. The dealer will be able to make the vehicle, with the aid of EOBD diagnostic equipment go into forced regeneration and clear filter. Don't run vehicles with diesel particulate filters on 100% bio-diesel only use EN 590. Only use low ash engine oil.
The DPF sensor has two pipes, these are connected to either side of the DPF this measures the pressure difference. If the filter is blocked the pressure difference will be greater and the ECU will try to make the DPF regenerate to clean itself.
Picture show Diesel Particulate Filter, you can see one of the DPF sensor pipes.