wiring Problem?

[codygood]

Alright guys i am new to this forum but i need some help. my dad bought a 2004 GMC Sierra 1500 4wd with the 4.8, runs an drives great, but the heat and 4wd work only sometimes, im gonna try to explain this the best i can, his heat works on 5 but no other setting when every thing works it works great 4wd works fine, heat blows hot, but when they both go out the Ebrake light comes on an ABS light comes on.. one second his heat is working then he will go to turn it off an it wont come on then them lights pop back up, any idea on wher eto start looking any help is highly appreciated, its getting quite aggravating we thought it might be the blower motor resister i unplugged it an the 4wd worked i plugged it backup 4wd is still working an heat was working, but you let the truck set an comeback to it an its doing the samething again. wehave changed the speed sensor, an the actuator its not blowing any fuses, its like its getting power an then just dont, he said one night hewasdriving home an his heat wasnt working an he hit a bump an it started working so its gotta be wiring related? a ground? giving you guys all the info i got at this point anything will help

[anumber1]

It's a bad ground. Check the bcm ground and the abs pump ground.

[codygood]

thanks for the quick reply, where is the bcm ground located? we have checked the abs ground

[codygood]

ive been researching could it have to do with the ignition switch? it seems to be a notorious issue

[codygood]

i think wemay have found the problem, the ignition switch i wiggled it an everything started working as its suppose to, plus it wasnt getting power with the key on which is why i am positive that is it

[anumber1]

i think wemay have found the problem, the ignition switch i wiggled it an everything started working as its suppose to, plus it wasnt getting power with the key on which is why i am positive that is it

Glad you found it!

[BusyB419]

Just an fyi. I replaced my ignition switch in 98 k1500 d/t the firing not staying running issue they cause. A couple years later I began having all the same issues you described. Banging tilting steering wheel is how I could get it to work, tranny wouldn't shift either. Turned out to be 7mm nut was loose that grounds ignition switch wire loom to bottom of column. Maybe that's all that is causing your problems. Loose nut???