Apparatus (100, 200) for testing a cable harness having a multiplicity of networks (151, 152, 251, 252, 265), which are formed by connecting elements (153, 154, 253, 254, 266) having individual contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273), which are coupled to one another by lines (160, 161), having: a signal generator (101, 201), which is designed to generate at least one test signal (102, 103, 202, 203, 210) at a prescribed frequency, a coupling apparatus (104, 105), which is designed to contact-connect at least one of the networks (151, 152, 251, 252, 265) by means of one of the contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) of the network (151, 152, 251, 252, 265) and to feed the test signal (102, 103, 202, 203, 210) into the corresponding network (151, 152, 251, 252, 265), and a testing unit (106, 206), which is designed to contact-connect the further contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) of the at least one network (151, 152, 251, 252, 265) and to test whether the test signal (102, 103, 202, 203, 210) at the respective frequency is applied to the further contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273); wherein the signal generator (101, 201) is designed to generate a test signal (102, 103, 202, 203, 210) at a prescribed frequency for each of the networks (151, 152, 251, 252, 265), wherein the coupling apparatus (104, 105) is designed to contact-connect each of the networks (151, 152, 251, 252, 265) and to feed the corresponding test signal (102, 103, 202, 203, 210) into each of the networks (151, 152, 251, 252, 265), and wherein the testing unit (106, 206) is designed to ascertain the frequencies, which are contained in the signals applied to the respective contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273), at the contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) that are not contact-connected by the coupling apparatus (104, 105); characterized in that the testing unit (106, 206) is designed to test whether frequencies, which are not fed into the network (151, 152, 251, 252, 265) of the respective contact (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273), are applied to the contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) that are not contact-connected by the coupling apparatus (104, 105); wherein the testing unit (106, 206) is designed to determine a coupling factor with respect to the corresponding further networks (151, 152, 251, 252, 265) for the contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) to which frequencies that are not fed into the network (151, 152, 251, 252, 265) of the respective contact (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) are applied. a signal generator (101, 201), which is designed to generate at least one test signal (102, 103, 202, 203, 210) at a prescribed frequency, a coupling apparatus (104, 105), which is designed to contact-connect at least one of the networks (151, 152, 251, 252, 265) by means of one of the contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) of the network (151, 152, 251, 252, 265) and to feed the test signal (102, 103, 202, 203, 210) into the corresponding network (151, 152, 251, 252, 265), and a testing unit (106, 206), which is designed to contact-connect the further contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) of the at least one network (151, 152, 251, 252, 265) and to test whether the test signal (102, 103, 202, 203, 210) at the respective frequency is applied to the further contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273); wherein the signal generator (101, 201) is designed to generate a test signal (102, 103, 202, 203, 210) at a prescribed frequency for each of the networks (151, 152, 251, 252, 265), wherein the coupling apparatus (104, 105) is designed to contact-connect each of the networks (151, 152, 251, 252, 265) and to feed the corresponding test signal (102, 103, 202, 203, 210) into each of the networks (151, 152, 251, 252, 265), and wherein the testing unit (106, 206) is designed to ascertain the frequencies, which are contained in the signals applied to the respective contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273), at the contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) that are not contact-connected by the coupling apparatus (104, 105); characterized in that the testing unit (106, 206) is designed to test whether frequencies, which are not fed into the network (151, 152, 251, 252, 265) of the respective contact (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273), are applied to the contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) that are not contact-connected by the coupling apparatus (104, 105); wherein the testing unit (106, 206) is designed to determine a coupling factor with respect to the corresponding further networks (151, 152, 251, 252, 265) for the contacts (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) to which frequencies that are not fed into the network (151, 152, 251, 252, 265) of the respective contact (155, 156, 157, 158, 255, 256, 257, 270, 271, 272, 273) are applied.