Hello all,

I have a 2000 Blazer LS, 2 door / 5 speed manual. It has the dash 4wd switch WITHOUT the auto 4wd function. Currently, 4-HI is illuminated on the switch. It will also switch into 4-LO without issue. If I attempt to switch into 2-HI, the light will flash and I can hear the Transfer Case Control Module clicking, as well as the transfer case trying to shift. After a few seconds the light stops flashing and 4-HI illuminates again.

Now where it gets a bit odd, and the reason I have not been able to find a definitive answer while searching: it appears the transfer case DOES shift into 2-HI even though the switch says it cannot. When I turn the front driveshaft by hand after pressing 2-HI, I can turn it easily. When I press 4-LO again, I cannot turn it by hand. Same with when I press 4-HI.

I replaced the dash switch to no avail. The control module seems to be working because I can hear the clicks. So, does this seem like a vacuum issue or possibly an issue with the signal that the encoder motor is sending to the module/switch? It seems odd to me that it has all the symptoms of being stuck in 4WD but mechanically, seems to be switching between modes just fine.

Thank you in advance for your help!