Are your doors locking with the remote? The locking mechanism is pneumatic could be a leak or even a corroded terminal on the sending or receiving unit and the signal to lock at speed is lost. The air pump is located in a pretty terrible spot. To locate it remove all the stuff in your trunk floor and under the foam on the passenger side is the unit. It tends to be subjected to moister being that the rear compartment vent is right there. I would have done the same as you by starting with fuses not to make you sound dumb I'm sure you looked but you do know that there are 2 sets of fuses one under the hood and one on the driver side behind the headlight switch right? Nothing like missing something this simple and dragging a problem out for weeks ya know lol