Hi everyone, I have a 94 4x4 Blazer with electronic engagement. I've read many threads but nothing seems clear on resolving the issue of 4-hi not engaging but 4-lo does. I have changed the vacuum canister under the battery, pulled and checked the vacuum sensor on the transfer case (both work fine) and checked the vacuum lines.
I can hear the TCCM "click" when I press 4-hi, but it does not engage at all although both the 4-hi and 4-lo lights are on. I've pulled the TCCM fuse, started the truck, replaced the fuse...no difference. Also unplugged the TCCM for 15 minutes, turned the ignition 5 times, still no change.
ANY help would be greatly appreciated! Thanks in advance

 

Encoder motor on the transfer case. I got one at the junk yard for $65 for our '96.

The actuator under the battery,vacuum switch on the t/c,and the vacuum lines are for engaging the front axle only.