The steering wheels with the radio controls have a different resistance for the cruise control buttons, your cruise control may not work with a newer steering wheel. I have an 06 steering wheel from a cummins conversion. I had to swap it to a wheel from an 00 to get the cruise working.
$150...
Sounds like you have a something shorting your 5 volt ref on that circuit. Unplug the egr valve that's the only one I've had short that circuit.
If that doesn't do it you'll need a wiring diagram to see what runs off that 5 volt ref.