A method pertaining to an SCR system for cleaning of exhaust gases from an engine (150). A dosing unit (250) is in thermal contact with the engine's exhaust system and supplies a reducing agent to an exhaust duct (240) of the exhaust system. Determining (s340) whether there is an undesired temperature level of the dosing unit (250). If yes, limit (s360) the temperature of the exhaust duct (240) by controlling operation of the engine. Also, a computer program product containing program code (P) for implementing the method. Also a device and a motor vehicle (100) which is equipped with the device are disclosed.