I Searched and read a lot here. I guess the Motor on the transfer case is suspect.
Here's the specifics: 99 Blazer 4 door. 3 switch system 2Wheel drive button is lit fine. Press 4WD Hi and the light lights when it is pressed but does not stay lit. At this time the 2WD light stays off. I can hear a relay click but no 4WD. I am old school and my other vehicles have Manual Hubs and Manual Shift levers. I am a bit familiar with the stupid Windshield wiper motor that Ford uses to shift their 4WD cars. Is this basically the same for this Blazer?
I read something ab TCCM codes? can someone help me with that? Is that part of the OBDII?

 

Completely separate from the OBD2 system. You can read the codes by following the information in THIS THREAD.

And it is not a glorified windshield wiper motor that is used here...

 

I just looked up the replacement motor to see what it looks like.
It is a unique design for transfer case shifting. I will never understand how the Manufacturers think. Wires and Connectors
in these High abuse areas. My '75 Jeep and my wife's '85 Chevy truck with manual everything has never let me down and they have 3X the mileage of this 100K mile Blazer. AND we are the origianl owners.
The snow is pounding down so I will have to buzz this out another day.
That's Pin #13 of the Gray connector. So it is te OBDII connector, but I am just shorting 13 to ground to get a specific TC diagnosis.