Diesel particulate filter (DPF) cleaning

The particulate filter (DPF) traps soot from a diesel engine's exhaust and burns it off by itself, in a regeneration, mostly on long drives at steady revs. If you mostly drive in town, regeneration doesn't finish, the filter clogs, the warning light comes on and the car can go into limp mode. The garage can start a forced regeneration with a diagnostic tool or remove the filter to clean it. Removing the filter for good is not allowed: the car no longer meets the emissions standard it was approved under.