Shielding maintenance of a complex cable harnesses which transmit measurement, control, or other type of signals to electronic shielded devices is a difficult and unsolved task in the electromagnetic compatibility community. Several methods have been developed for this purpose during the past years. The vast majority of these methods needs to dismantle and then reconnect the wired electronic system for maintenance test purposes. This paper presents and analyzes a new method based on immunity tests for shielding maintenance of wired electronic systems. The proposed method avoids the cable system disconnection and attacks the problem from the immunity point of view.