Method For Determining The State Of A Reducing Agent In A Reducing Agent Tank

A method for determining a state of a reducing agent used for exhaust gas post-treatment of exhaust gas generated by an internal combustion engine in a reducing agent tank, comprising:

• determining and recording filling and extracting quantities of the reducing agent from the reducing agent tank by a filling level sensor over an entire service life of the exhaust gas post-treatment unit;
• determining and recording a temperature of the reducing agent in the reducing agent tank by at least one temperature sensor over the entire service life of the exhaust gas post-treatment unit;
• determining and recording a propagation speed of ultrasonic waves in the reducing agent with an ultrasonic transmitter and ultrasonic receiver;
• and
• determining, in a control unit, the state of a reducing agent based at least in part on the filling quantity, the extracting quantity, the temperature, and the propagation speed of the reducing agent in the reducing agent tank.