I have a 2001 blazer with the np8 accutor motor for the transfer case, some months ago when the weather was bad i tried to lock the 4x4 in, the 4 hi button flashed but would not ingage, after trying several time the 4 hi locked in, however when i tried to go back into 2hi i couldnt, i disconected the battery and and tapped on the accutor motor and reconected the battery, pushed the 2hi button and the transfer case shifted into 2hi which is where i left it until i got a replacement for the accutor motor.

When i replaced the accutor motor i have the same symptons as before.
the blazer is stuck in 4 hi,
When i push the selector button the tccm clicks
the light flashes, the actuator motor hums but remains in 4 hi, it doesnt matter which button i select the blazer remains in 4 hi.
when i remove the fuss for the 4 wheel drive located in the dash the blazer is in 2 hi.

looking for any help.

 

*Moving to 2nd Gen Blazer Tech*

 

I am having the same issues, did you ever figure out what was causing the problem and how to fix it??

 

they have issues with the transfer case modules. also there is a vacuum actuator under the battery. sometimes the van lines rot out. but if your HVAC mode switch works. usually it will not lead to a vac leak with your actuator.

 

I had that issue.. I turned the key on, put it in neutral.. held the 2hi button n put the fuse in n out in n out in n out and it finally worked.. still dont know whats up with it, but it worked

 

When I had that issue in my 96,it was that junk dash switch with the foil contacts that fell apart every time I touched it with more pressure than a q-tip!