[rufcar]

they are on all the c4 zr1s. There are 2 one below the battery on the frame and one just on the opposite side. GM installed them in case of a front-end collision, it stops your fuel pumps from pumping and other electrical items just not sure how many. In the 90 zr1 the ground wire has a grounding problem; all newer year's GM solved the problem. It sets off the passenger seat blet light and ALDL light on your DIC screen. Its been talked about on this and many forums since inception. The fix is to remove the sensors, grind both surfaces to bare metal and reattach, then clear the codes. Mine came back so I added an additional ground to the metal firewall/door jamb area.