The relay is located in the trunk compartment, under the rear deck. There are 2 of them, one to activate firm ride, one for soft. Code 5 is the soft relay. I dont think they are serviceable. Sorry I dont know how to tell them apart, other than flip the switch and listen for either one to click. Good luck, JJ
PS, looks like it may be a pain to get to them with the subs in the way. You can also get to them by lowering the rear seats.