Suppose you are en route to your destination when your Garmin GNX375 competely fails. You don't have a second GPS and you don't have a second transponder but you do happen to have a NAV/CDI on board so you decide to shoot an ILS or LOC approach. However, the plate says "DME or RADAR required" and the GNX375 was your sole source of DME information. Since the GNX375 was also your transponder, does that also mean you can't fly the approach? Or can ATC legally be of service based off of primary returns?