Tony T, that very thing about the battery in the fob going out happened to a buddy and I about 2 & 1/2 years ago. We were in his 99 Dodge one ton, 2nd gen Cummins, it was a hot as h*#l July or August Saturday, and we were going to go into a Home Depot to get some item we needed to fix something, and he says we will leave the truck running so it will be cool when we come back, sounds like a plan to me. ! Got back to the truck in a couple of minutes, and low and behold, the key fob would not open up the door. Home Depot does not sell that size battery, surprise! He had to call his wife to come and get us, take us to Wally World camera department, get a battery, go back to the parking lot and open the door. Whole thing took a little longer than an hour, but the cab was cool! FWIW.