Method for determining an electrical fault of a conductivity sensor for ascertaining the electrical conductivity of a medium in accordance with the conductivity principle, wherein the conductivity sensor comprises a first electrode pair that is designed to be fully disposed in the medium and a second electrode pair that is designed to be fully disposed in the medium, wherein the method comprises: - applying an electrical alternating voltage to the first electrode pair, - ascertaining the temporal profile of the electrical alternating current at the first electrode pair resulting in response to the application of the electrical alternating voltage at the first electrode pair, - ascertaining a current-amplitude characteristic value of the ascertained temporal profile of the electrical alternating current, and - determining an electrical fault of the conductivity sensor if the ascertained current-amplitude characteristic value is below a first current threshold value or above a second current threshold value, wherein the method, if it was determined that no electrical fault of the first electrode pair is present, further comprises: ascertaining the temporal profile of the electrical alternating voltage at the second electrode pair resulting from the alternating voltage applied at the first electrode pair, - ascertaining a voltage-amplitude characteristic value of the ascertained temporal profile of the electrical alternating voltage at the second electrode pair, and - determining an electrical fault of the second electrode pair if the ascertained voltage-amplitude characteristic value lies below a voltage threshold value, wherein the determination of an electrical fault of the second electrode pair comprises: - ascertaining a phase shift between the alternating voltage applied at the first electrode pair and the alternating voltage resulting from it at the second electrode pair, - determining a short circuit between the electrodes (122, 124) of the second electrode pair if the ascertained phase shift lies below a predetermined phase threshold value, and - determining a break in one of the electrical supply lines to the electrodes (122, 124) of the second electrode pair if the ascertained phase shift lies above the predetermined phase threshold value. - applying an electrical alternating voltage to the first electrode pair, - ascertaining the temporal profile of the electrical alternating current at the first electrode pair resulting in response to the application of the electrical alternating voltage at the first electrode pair, - ascertaining a current-amplitude characteristic value of the ascertained temporal profile of the electrical alternating current, and - determining an electrical fault of the conductivity sensor if the ascertained current-amplitude characteristic value is below a first current threshold value or above a second current threshold value, wherein the method, if it was determined that no electrical fault of the first electrode pair is present, further comprises: ascertaining the temporal profile of the electrical alternating voltage at the second electrode pair resulting from the alternating voltage applied at the first electrode pair, - ascertaining a voltage-amplitude characteristic value of the ascertained temporal profile of the electrical alternating voltage at the second electrode pair, and - determining an electrical fault of the second electrode pair if the ascertained voltage-amplitude characteristic value lies below a voltage threshold value, - ascertaining a voltage-amplitude characteristic value of the ascertained temporal profile of the electrical alternating voltage at the second electrode pair, and - determining an electrical fault of the second electrode pair if the ascertained voltage-amplitude characteristic value lies below a voltage threshold value, wherein the determination of an electrical fault of the second electrode pair comprises: - ascertaining a phase shift between the alternating voltage applied at the first electrode pair and the alternating voltage resulting from it at the second electrode pair, - determining a short circuit between the electrodes (122, 124) of the second electrode pair if the ascertained phase shift lies below a predetermined phase threshold value, and - determining a break in one of the electrical supply lines to the electrodes (122, 124) of the second electrode pair if the ascertained phase shift lies above the predetermined phase threshold value. - ascertaining a phase shift between the alternating voltage applied at the first electrode pair and the alternating voltage resulting from it at the second electrode pair, - determining a short circuit between the electrodes (122, 124) of the second electrode pair if the ascertained phase shift lies below a predetermined phase threshold value, and - determining a break in one of the electrical supply lines to the electrodes (122, 124) of the second electrode pair if the ascertained phase shift lies above the predetermined phase threshold value.