02 ZF6 cruise/high idle inop

fdgefrts · January 5, 2021

Hello everyone,

I'm hoping someone has some schematics or diagrams for the cruise system on my truck. I've got an 02 LB7/ZF6 truck that I'm having some issues with. Here's the story:

Bought truck 2 years ago needing injector work- replaced injectors. While doing this I did the high idle mod and verified high idle and cruise worked as they should. I then pulled the cab/bed off for paint work and in the process of reassembling everything I broke the clutch switch- no biggy, ordered a new one and the truck starts as it should (no crank with no clutch depression, cranks when clutch is depressed). months after getting the truck together and driving it, I noticed the cruise didn't work- then it got cold and I noticed the high idle no long worked either. Everything else works fine though, truck runs great. The original multifunction switch had an issue with the wipers (wouldn't spring back from mist) so I replaced that hoping that might possibly solve both issues. The new multifunction switch seems to work great, but still no cruise control. In disconnecting the brake switch to troubleshoot that, the whole thing blew apart so I got a new switch- still no joy. The truck has LED brake lights/third brake light but I kept all my old incandescent lights and switched those in- STILL no luck! I'm at the point now where I'm kind of dead in the water without a schematic- I've already replaced every part I can think of that has to do with the system and as a technician myself I'm ashamed I haven't found the issue yet. As car as I Can tell all cab grounds are all good & connected, fuses all look good (I checked them with a multimeter) and the speed sensor works. This is a Texas truck with virtually zero corrosion anywhere. My 4WD light is on but I doubt that has anything to do with this. Would anyone happen to have a GM troubleshooting track or some diagrams that might help a brother get his high idle back? I miss it terribly

fdgefrts · January 7, 2021

I got this fixed. In case anyone else runs into this problem with one of these trucks, my problem was that my new clutch switch had a pin that wasn't making contact and sending the signal to the ECM that the clutch was released. I went in there with a pick and was able to bend it down a bit so it had continuity across pins E & F when the clutch was released.

Moral of the story- don't trust brand new parts.

Edited January 7, 2021 by fdgefrts