01' Blazer 4x4
4.3 liter v6
Automatic

When I press any of the 4 wheel drive buttons "4hi, 4lo, 4whl auto" I hear a relay click behind the dash on the passanger side but the 4 wheel drive does not engage and which ever 4 whl option I pressed the light just flashes. If I then press the 2 whl drive button it returns to the 2 whl drive solid yellow light.

 

I think it may be fixed. I found a broken vacuum line in the top center of the firewall and repaired it. Started it up and pushed the 4x4 button and it went into 4 whl drive and the light went solid.