2002 Blazer with the dash button 4x4 shifter. I have consulted the 4x4 no worky and other threads related to the t-case.

T-Case sounds like it’s working when mode and range shifting. Will clearly go into low range, but I’m not getting power to the front wheels in either range. LEDs on the shift buttons work as they should. Where would you start in light of the fact that it sounds like it’s engaging and the push buttons are lighting up as they should?

 

I'm not expert on these but here's where I would start...Under your battery is a vacuum actuated diaphragm. When your TCase is switched to 4WD, it gets vacuum and pulls on a cable that goes to the front differential and engages it. I would apply vacuum to that and see what happens. You should be able to find the feeder hose for that up top and view the actuator with a mirror or a borescope. I believe that the vacuum solenoid for all of that is on the firewall top and center. Actually, you could start with the solenoid and see that it's functioning correctly too.

 

So, a CEL just came on and the code is P0171. I am wondering if this is suggesting that the 4wd issue might be related to the P0171 code.

 

It was the actuator under the battery tray, but it had trans fluid in it so I replaced the switch too.