while towing up a long hill at 70mph, my throttle suddenly failed. 1996 6.5, 103,000 miles, otherwise bombproof for 8 years. The engine continued to idle, and in granny gear, I exited freeway for tow. By the time we took truck off tow truck, it worked perfectly. The computer diagnostics showed "failed throttle," and "service throttle soon" light came on. It is running perfectly now, but I bought a $450 throttle assembly just in case. the fuel pump was replaced a year ago. I had just finished installing a new water pump, and "may" have knocked a wire loose. Anyone have any ideas on what gives? thanks, Carl

it sounds to me like it may be your accellerator pedal. there is a switch on it that has three rheostat coils in it,(kind of like a dimmer switch). sometimes one of the coils may be bad and you will still have throttle response, here is the catch,you may lose response at a certain position on the acellerator. the next catch is that you cant buy just the switch that is mounted to the pivot point of the pedal assembly,(probably a seven dollar item) but you must go to the gm stealer and let them blackmail you into buying the whole assembly for like $300.00 u.s. had it happen to me, same symptoms. before you put new pedal on though, i would check the obvious first. check ops, do lift pump test, and check pmd if you have a spare. just takes a few minutes to eliminate those problems before you put on a part that may not be the problem. are you running a lubricant in your fuel? you may have sticking parts in your ip due to low sulfur diesel fuel. that may be your biggest culprit. try one quart of hydraulic fluid per tankful of diesel, not tranny fluid. hydraulic lubricates, tranny burns awful hot.

It could have a bad ground or 5v reference wire in the harness that intermittently short the curcuit.