A sensor and method for determining at least one internal parameter for an active sensor in a special mode of operation. The sensor has at least one sensor element, an evaluation circuit, at least two connecting lines, and a changeover module. The sensor is changed over between a normal mode of operation and the special mode of operation by means of the changeover module and is put into the special mode of operation for the purpose of determining the at least one internal parameter. The sensor has an electric offset source which is used in the special mode of operation to at least partially actuate the evaluation circuit on the basis of the supply voltage of the sensor which is applied to the two connecting lines such that the at least one internal parameter of the sensor can be ascertained from the sensor output signal.