In a method and a device for adapting the injection agent supply for an emission control system, the following steps are carried out: a) setting of a agent pressure target value in the line upstream of the pump in relation to the ambient pressure; b) opening of the pressure relief valve for a predetermined time t; c) determining the pressure difference between the target and the injection agent pressure, caused in step b), immediately after step b); d) setting a target value for the agent pressure in the line downstream of the pump in relation to the exhaust gas pressure in the system; e) opening of the injector for a predetermined time t; f) determining the pressure difference between the target and the agent pressure, caused in step e), immediately after step e); g) comparing the pressure differences from steps c) and f); and h) optional adaptation of the injector opening time.