Got 4 lights on this morning

I would put money on the wiring to the diff lock switch (sensor), or the sensor itself.

When the sensor says the diff is locked, the 'diff lock symbol' on the dash will be on (solid, not flashing). Locked diff locks out ABS, TRAC...

If the ECU detects that the diff lock sensor shows locked, while the ECU is commanding unlock, it will eventually code and lock out 4wd mode changes. The code will go away on restart per my recollection, but will come back after X miles and Y starts, etc.... I am guessing switch is stuck on, or damaged, or frozen...

I would disconnect the lock sensor wire on the diff (BLUE and BLACK wire connector per my recollection on the diff, NOT the red and black), and see what happens. Check that switch with an ohmmeter.

That is my best shot from the hip... Seems like it hits all your symptoms, but obviously I am just guessing based on what you posted.

 

BigWhiteTRD, that seems to make sense actually. Over the weekend i continued to fight with it, but sometimes instead of those 4 lights coming on, there would be a message saying "2WD/4WD mode change failure". Then i would restart the truck and everything would be working flawlessly. Everything is working fine this morning, but there's no guarantee this afternoon.

 

On this episode of 'Stump the Chumps'...
Any conclusions, learn anything?

 

BigWhiteTRD, i havnt looked into the problem since it first started but i just check the sensor with an ohm meter and its reading 1. im not sure what its supposed to read if its working right...

 

First check your ohmmeter to see if it is working right.

(Touch probes together and should read less than 1 ohm, ideally 0.1 ohm or so. Next hold probes in free air and should read 1 on the left of the screen, which means the resistance is higher than can be measured, essentially infinite resistance).

The lock switch should be open (infinite resistance, flashing '1' on left typically) with diff unlocked.

So if I am understanding, yours sounds like it is measuring correct. Need to check when the truck is pissed at you, see if still reads open.