A method for operating an exhaust gas treatment device having at least one reservoir for a reducing agent and at least one delivery device for a reducing agent, includes at least checking a filling level of the at least one reservoir, checking a current exhaust gas mass flow, and delivering reducing agent if the filling level of the at least one reservoir is below a minimum filling level and the exhaust gas mass flow is in a low-load range. A motor vehicle having the exhaust gas treatment device is also provided.

A device for lambda control of a gasoline engine includes a first three-way catalytic converter, a second three-way catalytic converter, a linear lambda sensor, a binary lambda sensor and an NOx sensor. The first three-way catalytic converter is arranged upstream of the second three-way catalytic converter. The linear lambda sensor is arranged upstream of the first three-way catalytic converter. The binary lambda sensor is arranged downstream of the first three-way catalytic converter or the binary lambda sensor is arranged in the first three-way catalytic converter or in the second three-way catalytic converter and is arranged upstream of the second three-way catalytic converter. The NOx sensor is arranged downstream of the second three-way catalytic converter, and the linear lambda sensor, the binary lambda sensor and the NOx sensor are connected to a control device for lambda control.

A system includes a controller having at least one processor coupled to a memory storing instructions that, when executed by the at least one processor, causes the controller to: receive data indicative of operating conditions of at least one of an engine or of an aftertreatment system; determine, during a first period of time, that an amount of NOx output from the aftertreatment system satisfies a low NOx operating mode condition based on the data indicative of operating conditions; determine, during a second period of time, that operating conditions for a conversion efficiency are present based on the data indicative of the operating conditions of the aftertreatment system; determine that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition; and selectively set an alert based on a retrieved minimum value and a retrieved maximum value of the amount of NOx outputs.