2000 gmc jimmy blowing the atc fuse

[midnights00]

I have a 2000 gmc jimmy that keeps blowing the atc fuse. It was stuck in 4 hi so I changed the transfer case motor and it started blowing the fuse. I checked the module behind the kick panel and it was corroded. I took it off and cleaned the plugs and the module and reinstalled it. It worked in the garage but when I left the garage it blew right away. The canister under the battery box works I believe because I could unplug the electronic vacuum control on the firewall and it would disengage my front differential. If I plugged it back in it locked the differential up again. Wondering if anyone has a clue? I don't really know where to go from here.