My 2003 Blazer somehow got locked into 4WD Hi. Attempts to put it into 2WD or 4WD low do nothing. The 4WD Lo light is on immediately when engine started and nothing blinks when 4WD Low or 2WD is selected. There are no error lights lit.
I have disconnected the battery for 30 minutes with no change. Does this mean the encoder motor is bad?
How can I get it out of 4WD?

 

3-button or 4-button switch? You can take off the transfer case shift motor and shift it manually.

 

I removed the encoder motor to inspect it and and saw no corrosion. I plugged it back in to the connector to visually see if the motor was rotating the drive - and it rotated when I pushed the 2HI button with the engine running. I then rotated the transfer case to neutral manually, adjusted the encoder drive and reinstalled it. It is working normally again. Apparently removing the electrical connector reset everything.