Truck Repair: trailer lever brake and high idle not working, frightliner, mechanical check

Question
thanks in advance.
i have a 2001 frightliner century which has a detroit 430 60series, suddenly last week the high idle started not wanting to work all the time and finnaly wont high idle anymore(the cruise control still works) also the lever to apply only the trailer brakes dont work, i really hope you guys can help me.
god bless.

Answer
The high idle is a computer controlled feature -- an diagnostic scan tool will help to narrow down your problem ---  The brake lever not working is another story that is an air controlled unit -- mechanical -- Check the air supply to the hand valve --