4x4 engaging at ADD actuator and then disengages

Hello Tundra owners. I’ve got a long story about my current situation. I’ll explain the short and simple first then add the long story afterwards if you want to read the details.

This is my friends truck. He went to the dealer and they did the diag. They checked the switches and 4x4 ecu.
2008 Tundra 5.7. 4x4 wasn’t working at all. All the lights were on. 4hi, 4lo, traction control, abs, etc.
They said the transfer case actuators needed to be replaced so the transfer case had to come out. He didn’t want to pay that so he got the actuators and we replaced them.
4x4 Still wouldn’t engage. All the lights went away except for the 4hi blinking when turning the switch 2wd to 4hi.
We noticed nothing coming from the ADD actuator so we replaced that. Before replacing the ADD actuator 4x4 wouldn’t lock the front driveline.
After replacing the ADD actuator 4x4 will engage but disengage.
This is were we’re at now.
Initiate 4x4 switch, you can hear the transfer case actuator motor turn on, the ADD actuator fork slides the slider to lock the front diff, after about 10 seconds the TC actuator motor turns on and the 4x4 disengages. I know because I can spin the driveline when it was previously locked.
No CEL’s. 4hi does blink slow when engaging (initial TC actuator turns on) in 4x4 but blinks fast after it disengages 4x4 (when you hear the TC actuator turns on again to disengage 4x4).
I have been searching for sometime and have found a lot of different 4x4 threads but nothing about my current situation. I also found the 4x4 diag pdf, that will be the next step.
We reset TC actuators using a procedure found on YT from a person on this forum.
I just find it discerning that everything seems to be working but something is telling the 4x4 ecu to disengage when everything is locking into place.
I was hoping someone may know something I’m missing.

 

Check the ADD switch to make sure it is closing when the ADD is engaged. You could do this by engaging the transfer case and ADD. When ADD is engaged pull the negative on the battery so it stops any actuator movement. Then pull connector off of ADD and measure resistance between pin 4 (ground) and pin 3 (ADD switch) on actuator. Should be zero ohms or close. If thats ok measure resistance from pin 4 on the plug to ground. This should be zero ohms. If thats ok messure from pin 3 of ADD plug back to the 4 wheel drive ECU to check continuity of the wire.