Method for flushing a pressure line of a delivery device

A method for operating a device configured to convey an aqueous urea solution in a motor vehicle, having a conveying device which has a pump for conveying the aqueous urea solution, comprising:

• in a first conveying process:
• operating the pump in a first conveying direction to convey aqueous urea solution to at least one injector;
• and
• conveying the aqueous urea solution from a tank via an intake line, through the conveying device, to the at least one injector, arranged outside the conveying device, via a pressure line, wherein the at least one injector is arranged on an exhaust-gas line and is configured to inject the aqueous urea solution into the exhaust-gas line, wherein a bypass leads to the tank from the pressure line, from a point upstream of the at least one injector;
• in a second conveying process, after the first conveying process has ended:
• closing the at least one injector;
• and
• operating the pump in a second conveying direction, which is opposite to the first conveying direction, opening the at least one injector for a predetermined period of time;
• drawing air into the pressure line through the at least one injector, wherein the air drawn through the at least one injector is drawn into the conveying device;
• and
• in a third conveying process:
• operating the pump in the first conveying direction while the at least one injector is closed, wherein the air drawn into the conveying device is pushed along the bypass to the tank.