stuck in 4low

[Pooble]

Have an 03 gmc 2500hd that ive been slowly rebuilding and just passed inspection it used to have service 4wd untill i cleaned up the driver side grounds and started to shift fine atleast long enough to pass, until today it shifted by itself into 4low by itself once i turned the truck on now it will not come out even in neutral tried going R-N-D-R-N...etc to kick it back on but no luck, confirmed it wasn't the 4x4 selector buttons, its not pulling any codes atleast on my scan tool. hitting up the junk yard tomorrow just going to grab a used tccm, actuator off the front diff and transfer case shift encoder since they are all super easy to pull and dirt cheap at my local junk yard and i have nothing but time at the moment.

 

just wondering if any of you guys have had good/bad luck with any of those parts failing on you and causing the truck to get stuck into 4low/hi or the truck shifting into those selections by itself. and what your fixes and problems were. thanks guys!

Edited February 23, 2024 by Pooble

[richard wysong]

It wouldn't be the front diff actuator, that just engages / disengages the gear in the axle. sometimes they get stuck due to corrosion around their threads. Try disconnecting the battery for a few minutes and see if it resets.You may need a better scan tool to get into the transmission/ transfer case. Is there oil in the transfer case?

[Pooble]

bit of an update it popped out of 4low this morning it shifts fine now but  service 4wd its back on the dash, and when i start the truck it starts it seems to pick a random setting(auto, 2hi 4hi/low). im going to check and and change the fluid out before i throw parts at it, double check my ground wires. and take a good look at the wiring and case.

[hiking_mike]

I forgot to mention, check the grounds. The main one is under drivers side door at the frame. 

I have an 07 LMM and ever since we got the windshield replaced, I think water ran down to the transfer case control module.

I have a new pne, but cant seem to understand the pics in All Data as to where the transfercase module is. I looked and I cant seem to get in there to be able to see how to remove.