Hi, I write this in the hope that an experienced Audi mechanic or an enthusiast might be able to help. The problem is with my son's Audi A3 2.0 TDI 170 Quattro which was taken into an Audi dealership after the DPF light came on and then went into limp mode when the DPF would not regenerate. Audi attempted to carry out a forced regeneration but found that the DPF was too clogged with soot. A new DPF was fitted along with a sensor but the warning light re-appeared the following day so the car was returned to Audi. After an inspection, Audi suggested that the problem would be due to one of three sensors, I do not know which three exactly but Audi told my son that they would fit the parts in the order in which they thought would be most likely to fix the problem. This was at my son's cost and he was told that the parts cannot be removed once fitted. The fault remained after all three items had been fitted. The next suggestion was to examine the insides of the engine which unfortunately revealed a worn turbo, a cracked cylinder head and damage to some valves which have also now been replaced. Audi have tested the car on a long journey and guess what? Yes, the DPF light came on and the DPF would not regenerate, apparently due to not reaching a high enough temperature. There is now talk of a new ECU being required! Is it possible for the existing ECU to be reset/reprogrammed instead of being replaced? Does anyone have any idea what might prevent the DPF from reaching a high enough temperature to allow regeneration? Have any readers had any similar experiences? If so, how was the problem resolved? My son is at the end of his tether and his Mother and I do not know how to help him other than telling him to trust the might and knowledge of Audi. This is turning out to be flawed and costly advice. Any suggestions/ideas would be most welcome. Thanks for taking the time to read this.