Methods for operating an SCR system and SCR system

Abstract

The invention relates to a method for operating an SCR system comprising a fluid tank for a fluidic reducing agent, a metering module for dispensing reducing agent into an exhaust system of an internal combustion engine, a supply module for conveying the reducing agent from the fluid tank to the metering module, wherein the supply module has a fluid pump and a main filter through which the reducing agent flows when passing the supply module, and a pressure line between the supply module and the metering module.The procedure includes, after changing the main filter, filling (311) the pressure line by operating the fluid pump in a pumping mode to pump reducing agent from the fluid tank into the pressure line, checking whether reducing agent is in the pressure line, if it is found that reducing agent is in the pressure line, stopping the filling, waiting (312) for a predetermined dissolution time (tA), after the predetermined dissolution time (tA) has elapsed, returning (313) reducing agent from the pressure line to the main filter, stopping the return, and waiting (314) for a predetermined settling time (tg).

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