Method for monitoring an ammonia slip catalytic converter

A method for monitoring an ammonia slip catalytic converter arranged in an exhaust gas after-treatment device of an internal combustion engine, downstream of a catalytic converter arrangement, wherein the method comprises the steps:

• measuring, by a first sensor, a nitrogen oxide content in the exhaust gas upstream of the ammonia slip catalytic converter, wherein the first sensor is positioned upstream of the catalytic converter arrangement and is configured to detect the nitrogen oxide content in the exhaust gas prior to the catalytic converter arrangement,
• detecting, by a controller, a sensor signal of an ammonia-cross-sensitive nitrogen oxide sensor arranged downstream of the ammoma slip catalytic converter,
• checking, by the controller, whether the ammonia-cross-sensitive nitrogen oxide sensor measures a value higher than the nitrogen oxide content in the exhaust gas measured by the first sensor,
• determining, by the controller, an operating condition of the ammonia slip catalytic converter based on whether the ammonia-cross-sensitive nitrogen oxide sensor measured the value higher than the first sensor, and
• outputting, by the controller, the operating condition of the ammonia slip catalytic converter as to whether the ammonia slip catalytic converter is functionally capable or defective.