2003 v8 trailblazer 4x4 issue

what i have is when i try to engage the 4x4 i turn the switch at the dash and the light changes to 4x4 and flashes like its going to engage. but then it goes back to 2wd without moving switch back. 4x4 does not engage. this happens with all settings awd and 4low. the service 4x4 light is not on and the 4x4 fuse is good. any help would be great we got snow tonight here in st louis!!! thanks!!! mark.

what i have is when i try to engage the 4x4 i turn the switch at the dash and the light changes to 4x4 and flashes like its going to engage. but then it goes back to 2wd without moving switch back. 4x4 does not engage. this happens with all settings awd and 4low. the service 4x4 light is not on and the 4x4 fuse is good. any help would be great we got snow tonight here in st louis!!! thanks!!! mark.

You'll need to get the codes from the TCCM (Transfer Case Control Module) Most likely you have a problem in the encoder circuit, which is part of the motor that shifts the transfer case. Need the code(s) to be sure.