Sounds like the "Body Controller" unit. The body controller monitors all of the possible sources of an "unlock" or "lock" signal. It monitors a radio frequency and unlocks the doors when it receives the correct digital code from the radio transmitter in your key fob, and also monitors the switches inside the car. When it receives a signal from any of these sources, it provides power to the actuator that unlocks or locks the doors.
It is located on the drivers side firewall under at the cab.
It is located on the drivers side firewall under at the cab.