Bob
Does the fast idle work?
Fast idle is a function of the cruise system programming in the ECM if the fast idle works the cruise problem is likely in the trigger circuitry and as others have pointed out the clock spring and switches are likely culprit's.
In my experience ECMs don't die they are murdered usually by an unwitting tech improperly testing or back feeding circuits .
Your local CAT dealer with CAT et. Software can use the software to monitor the inputs from your coach wiring to determine if the trigger signal is active and working.
Or as Fred pointed out you can check the clock spring and smart wheel by following the diagnostic procedure found in the coach assist .
Hope this helps
Eric
