The cruise control, steering & instrument package etc is created by the chassis manufacturer.
I have an 04 Freightliner chassis so may not be of much help, but there is an item in one of my fuse panels that's called a 'Cruise Disengage Relay.' Not sure what it does or if you have one, but it's the only thing close I could see in my manual.
I'd suggest you call Freightliner at 1-800-FTL-HELP (have your VIN #) and they can probably assist you. They are very helpful.
Ed & Joie
2004 Vectra 40KD
Freightliner Chassis and Cummins ISC