The truck will need to go to the GM dealer so they can reprogram the passenger door module (the window switch assembly is the door module and also controls the remote function actuation). Here is the applicable bulletin from GM.
#03-08-52-001C: Remote Keyless Entry (RKE) System Inoperative (Reprogram Passenger Door Module) - (Mar 17, 2003)
This bulletin is being revised to provide the latest service information. Please discard Corporate Bulletin Number 03-08-52-001B (Section 08 -- Body and Accessories).
Some customers may comment on any of the following conditions:
Important: For clarification purposes, the following information is provided. The components involved in this bulletin are known by various names. The Service Information Document ID #849813 refers to the component as the Door Lock and Side Window Switch. General Motors Service Parts refers to the components as SWITCH DR LK & SI WDO. Within this component is a micro processor that is referred to as the Passenger Door Module (PDM). Techline equipment refers to the component as the PDM Passenger Door Module. This bulletin addresses issues with the software of the microprocessor in the Passenger Door Module (PDM).
Perform the following procedure step by step (do not skip a step) to determine the proper course of action.
Important: Verify the software version in your Tech 2. If the software is not 23.001 or newer, your Tech 2 software needs to be updated.