4WD and 4-Lo indicators flashing

On the night of the Superbowl, I started my truck and my 4WD and 4-Lo icons started blinking and it's been this way ever since. The only thing I had done that was out of the ordinary was hit a car wash to get rid of the snow and salt residue on my truck earlier that day. I hadn't tried to engage my 4wd in a few weeks, and since then I have tried and there's absolutely nothing happening. I can hear the "click" of what I assume are two relays in the ECU closing every time I start my truck. I've been poking around and I tested the two sensors on the actuator by the T-Case, and those test fine. The 20a fuse tests ok. Any suggestions on where to check next? Thank you!

I also wanted to add the truck is not stuck in 4WD, the snow we've been getting here lately has made me very aware of that and missing this system working even more

 

Start here

 

Thank you, very helpful.

 

Did you have any luck getting yours fixed?

 

I've been lazy about fixing this since I haven't needed the 4WD. Lights have been flashing for months now but I just went out and tested today. So my selector switch is in H2 while all of this is going on, and my readings were all in line with that diagram you sent. The two readings that didn't match up were 2-4 reads 10v, and TL3 was only reading 11v. I'm more concerned about the 2-4 being open when it should be closed, do you know what that circuit goes back to?