A processing system comprises a sensing module, a first internal diagnostic mechanism, and a determination module. The sensing module is configured to couple with a first sensor electrode path of a plurality of sensor electrode paths, wherein the sensing module is configured to drive the first sensor electrode path with a first signal. The first internal diagnostic mechanism configured to couple with a second sensor electrode path and configured to acquire a test signal output while the sensing module drives the first sensor electrode path with the first signal. The first internal diagnostic mechanism comprises a selectable current source configured to couple with the second sensor electrode path, and wherein the selectable current source is enabled during acquisition of the test signal output. The determination module configured to determine whether the first and second sensor electrode paths are ohmically coupled together based on the test signal output.