On my 99, the shock sensor is under the steering column. You must remove the plastic panel that covers the column first. You also cannot see it at first, and must next remove the metal knee bolster panel, or stick your head back there by the pedals and look for it to see it.
Sensitivity is set from GM at the factory, but my guess is it has fallen off its mounting and not upright. You can adjust the sensitivity once you get to it if you want that is with the set screw. It is a small black plastic box.
I discovered mine while doing something else but noticed I think the way it came from GM was with double sided tape holding it on. Naturally as the tape ages, it falls off. Mine was duct taped in place, I used velcro to hold it better. The proper placement is connector pointed towards the floor.
