Procedure to diagnose an exhaust gas treatment device and device to implement the procedure

Abstract: A procedure for the pressure diagnosis in a reagent substance metering system, which introduces a reagent substance into an exhaust gas area of an internal combustion engine upstream in front of at least one exhaust treatment device as well as a device to implement the procedure is proposed. The reagent substance pressure occurring between a metering valve and a security valve disposed downstream after the metering valve is measured during different operating conditions of the metering valve and/or the security valve and is compared with at least one threshold value. An error signal is provided when the threshold is exceeded. The procedural approach according to the invention allows for a leakage diagnosis of the reagent substance metering system. Furthermore, the procedural approach according to the invention allows for a diagnosis of metering valve and/or the security valve and/or the check valve. The procedural approach according to the invention contributes overall to the elevation of the security, especially if the reagent substance is combustible. (end of abstract)