Patent ID: 8573043

Claim:
A method for monitoring an SCR catalytic converter ( 12 ), in which method the NH 3 storage capacity of the SCR catalytic converter ( 12 ) is monitored, with the SCR catalytic converter ( 12 ) initially being filled in an overdosing phase with a superstoichiometric reducing agent dosing up to the maximum NH3 storage capacity, subsequently being acted on in an underdosing phase with a reducing agent dosing which is reduced or is eliminated in relation to a normal dosing, and with the NH 3 storage capacity being indirectly determined during the underdosing phase by determining at least one characteristic value which is dependent on the NO x conversion rate, characterized by continuously measuring, during the overdosing phase, a variable which is characteristic of the NOx conversion, and inferring that NH 3 slippage ( 25 ) is present, indicating a transition from the overdosing phase to the underdosing phase, when the NOx conversion falls.