I just bought my grandpas 03 silverado 2500hd two months ago. The 4wd doesn't work, the front accuator, tccm, tc shift motor, selector switch, fuses and ground wires have all been tested or replaced and still nothing. I have the chiltons manual on its way for the wiring schematics, are there any other relays or fuses I should test before I start probing the wiring harnesses? Thank you for your help

 

Is this push-button 4WD? You did check the actuator motor on the transfer case?

 

Yes it is the push button 4wd. I did swap the TC shift motor with my neighbors working motor, it didnt work on my truck, then i checked my shift motor on his truck so I know for certain both shift motors work, just not on my truck. I now suspect it is either a relay, if there is one for the 4wd, or a wiring issue.

 

I'd check all the fuses first, of course.

Color coding for 2003 Chevy 2500 HD wiring is:

wire 2WD 4WD low
tan 14.9 14.4
org 3.1 3.0
drk blu .73 .70
yel 4.1 4.1
ppl .00 .04
whtgrn 7.5 7.5
tan 2.7 3.0
redblk 14.5 14.5

Here is the wiring diagram: Use Chrome or Microsoft Edge. Firefox won't read it correctly

https://www.silveradosierra.com/resources/file/149218

From what I read, it is usually the switch itself, runs about $19-to 27 USD or the TCCM at $264 USD.

 

Thank you for the schematic, that will help a lot when I get an actual day off. I will update if I ever get it working again.