you know, i had the same problem with my 02 rcsb.

when i first got it, it had a new headlight/blinker/cruise stick installed, the blinkers and whatnot worked fine but the cruise didn't work at all. never. i got so pissed off i started checking fuses, pulled the cover off the make sure everything was plugged in. nothing. and then it dawned on me. . . . manual windows and doors, no side moulding, steel wheels. hell this is a base model truck, i bet it doesn't even come with cruise. sure enough, i popped the hood and there were empty studs on the firewall where my cruise control module should be and only one cable on the TB.

so i tell people i saved weight by not getting cruise.