Individual wire defects in a data transfer/communication system that employs differential signaling can be detected during connectivity verification of a link prior to link training by individually disconnecting wires by wire polarity and testing the link. For example, the positive transmit wire of a lane may be verified by disconnecting the negative transmit wire of the lane and performing link connectivity verification. If the link passes connectivity verification, then the positive transmit wire of the lane is functioning normally. Connectivity of the negative transmit wire of the lane may then be verified by disconnecting the positive transmit wire of the lane and determining if the passes the connectivity verification.