When soot hardens into ash (crystallization), it blocks the exhaust flow, often triggering a "limp mode" where the car loses power. The accompanying dashboard message "HOT-" usually refers to a Transmission Hot Engine High Temperature
A generic scan tool cannot perform these service functions. P2df000 Volvo HOT-
The "useful story" behind this code is one of . Your car’s exhaust system needs to reach high temperatures to burn off soot (a process called "regeneration"). Because of those short trips, the engine never gets "hot" enough to finish the job. Instead of burning away, the AdBlue fluid starts to dry out and form white, rock-hard crystals—much like limescale in a kettle—eventually choking the exhaust. How to "Thaw" the Problem When soot hardens into ash (crystallization), it blocks