The 4wd in my tb ext is not working. It stopped working last winter. I'm not entirely certain what the issue is. My normal shop I go to when I can't do something myself charges $90 to read the 4wd code. The light in the instrument cluster is on. The light on the switch all work. I believe I should hear two sounds when switching into 4wd, correct? I only hear one. I'm not sure if it's the disconnect, switch, tccm, or encoder. Is replacing the disconnect a pretty straight forward swap? If I get a disconnect ($400 new; $100 used), can I simply plug the wiring harness in to test it to see if that's the issue or does it have to be fully installed? If the later is true, I will just get the code read first which is what I should do anyway. Is $90 about right to read the code? Thanks in advance.