A replacement test module for a test system, wherein the test system has two interfaces (16a,b) for connecting a respective test module (18a,b) and the test system is arranged to test a cable harness connected between the interfaces (16a,b) at least for electrical continuity (E,F) of its wires, wherefore the wires are electrically connected with their contact ends (8a,b) between the interfaces (16a,b), - having a counter-interface (20a,b) for connecting to one of the interfaces (16a,b) of the test system, - having at least one contact (62a-d) for electrically contacting a respective contact end (8a,b) of the cable harness, - having an electrical main line connecting the counter-interface (20a,b) to the contact (62a-d), through which electrical main line a measurement current generated by the test system flows during the operation of said test system, - having a good value for the measurement current, which can be specified with respect to the test system, - having a threshold for the measurement current, which can be specified with respect to the replacement test module and which is less than the good value, - wherein the replacement test module includes a control unit which is arranged - to operate the replacement test module at least in an active test mode in which: - an actual value of the measurement current generated by the test system, flowing through the main line is determined, and - in the event that the actual value is above the threshold, - on the main line a sum current is drawn in or output at the contact (62a-d) or the counter-interface (20a,b) as the correction end (79a,b) of the replacement test module, which sum current is composed of the measurement current and a supplementary current which is additionally discharged from or fed into the main line with a specifiable supplementary value, wherein the supplementary value is dimensioned such that the value of the sum current drawn from the test system or returned to the test system at least assumes the good value, - wherein the correction end (79a,b) faces that interface (16a,b) of the test system, which leads to an evaluation unit of the test system, - otherwise: - the measurement current is output unaltered at the replacement test module on the main line; the replacement test module is characterized in that the contact (62a-d) includes a brush unit in which the respective contact end (8a,b) of the cable harness can be received and electrically contacted, wherein the brush unit has electrically conductive bristles for electrically contacting the contact end (8a,b) in a mechanically protective manner. - having a counter-interface (20a,b) for connecting to one of the interfaces (16a,b) of the test system, - having at least one contact (62a-d) for electrically contacting a respective contact end (8a,b) of the cable harness, - having an electrical main line connecting the counter-interface (20a,b) to the contact (62a-d), through which electrical main line a measurement current generated by the test system flows during the operation of said test system, - having a good value for the measurement current, which can be specified with respect to the test system, - having a threshold for the measurement current, which can be specified with respect to the replacement test module and which is less than the good value, - wherein the replacement test module includes a control unit which is arranged - to operate the replacement test module at least in an active test mode in which: - an actual value of the measurement current generated by the test system, flowing through the main line is determined, and - in the event that the actual value is above the threshold, - on the main line a sum current is drawn in or output at the contact (62a-d) or the counter-interface (20a,b) as the correction end (79a,b) of the replacement test module, which sum current is composed of the measurement current and a supplementary current which is additionally discharged from or fed into the main line with a specifiable supplementary value, wherein the supplementary value is dimensioned such that the value of the sum current drawn from the test system or returned to the test system at least assumes the good value, - wherein the correction end (79a,b) faces that interface (16a,b) of the test system, which leads to an evaluation unit of the test system, - otherwise: - the measurement current is output unaltered at the replacement test module on the main line;