Mine was pretty obvious- wet floorboard, and surrounding areas. But the fuse box didn't look like it had seen water. However, once I removed the GEM module, it was pretty evident that it had gotten wet. I could see corrosion and water spots on the circuit board. Eventually, my wipers stopped working and I had to replace the GEM. Mine is just a work truck, so everything is manual, but like Hangemhigh stated, it seems like EVERYTHING runs through the GEM module. I believe I would get an airbag and seatbelt chime at,random times as well. I think the back side of the fuse box has a tendency to corrode as well- I had to remove the fuse box and disassemble it to see the back side. It looked fine from the front.