2017 GMC Acadia Denali. So out of the blue, after visiting a Walmart on a rainy day, my service park assist light went on. Never had any electrical issues prior. I figure someone hit a sensor so hard with a cart that it stopped working. Only issue is I don't know which one is defective. So my first question is, any way to figure out which is defective prior to ripping off the whole bumper, second my suv has front and rear sensors, so imagine u take off the bumper and then figure it it's the wrong bumper???!! Any ideas how to narrow down the search for the defective sensor front or rear and which one? I've seen some you tube videos on testing them by the clicking noise but out of all eight sensors I hear no noise at all.