P2002. Please help!

[Wiggy]

Hello. Im really struggling with a dpf fault code. Im getting the p2002 ( efficiency below threshold) code. I think the dpf has been removed by a previous owner as there is a non factory looking weld running around the dpf casing and she does smoke a little under acceleration. I have replaced the exhaust pressure sensor and i know the pipes are not blocked. It was running fine until i thought id get the turbo hot on a bypass to clean it. I have tryed resetting the values but cant seem to access coding through vcds. The car has gone into limp mode. Any help would be much appreciated as im at a loss and am considering selling the car as is.