Method and device for inspecting and safeguarding a functionality of an exhaust gas aftertreatment system of a combustion engine

A device for checking and ensuring functionality of an exhaust gas aftertreatment system of an internal combustion engine, the exhaust gas aftertreatment system includes a catalytic converter and a voltage source, the catalytic converter having a catalytic converter area and an electrical heating device which is selectively supplied with electrical energy from the voltage source, the device includes a control unit configured to:

• determine an actual value which is characteristic of an ohmic resistance of the heating device, the actual value based on an electrical current strength supplied to the heating device and an electrical voltage supplied to the heating device from the voltage source;
• determine a setpoint value which is characteristic of an expected ohmic resistance of the heating device, the setpoint value based on a specific heating-up behavior of the heating device and an expected long-term behavior of the catalytic converter, the expected long-term behavior mapping a service life of the catalytic converter;
• and
• compare the actual value with the setpoint value by:
• determining a first difference from the actual value and the setpoint value;
• and
• comparing the first difference with a first threshold value;
• and
• determine a fault based on the comparison, when the first difference deviates from the first threshold value by at least a first specific amount, the fault is indicative of the heating device not functioning in accordance with the specific heating-up behavior and the expected long-term behavior.