2wd to 4wd failure

I feel your pain but when mods are made under warranty you take a big chance that nothing will go wrong.
Cheaper to have the installer work on it.

 

Are you trying to engage 4wd while rolling? there is an order of operation. the front axle has to engage before the transfer case will shift. Front axle may have a hard time engaging with the locker in there. going into 4wd high while rolling may get the axle engaged and then going into low range when stopped may allow the shift to 4wd low. If the axle doesnt engage then no shift to 4wd in the transfer case. I'd be curious to see if the transfer case will shift with the driveshaft is out. This fly by wire crap doesnt help. Bring back the manual hubs and lever shift transfer case.

 

I'd put a pipe plug in it and not say anything.

 

The way I understand ADD, the transfer case actually engages the front driveshaft before the front axle is splined together. The reason - if the ring gear in the front diff is not turning (ie fed power from the transfer case), the driver's side axle shaft (through the carrier side gears) will cause the passenger side "stub" axle (before the actuator) to rotate in the opposite direction of the rest of the axle that's connected to the passenger side wheel = very little chance of splining together, since there's no synchro or whatnot in there.

Order of operations -

1. Flip switch on dash to 4HI, this goes to some computer or another, probably over CANBUS

2. If conditions are met, computer commands TCase to engage front driveshaft

3. when engaged successfully, TCase tells computer - yo, it's done.

4. Computer then commands front axle to connect the two passenger side axle halves, since they are spinning in the same direction now.

5. When connected successfully, front axle tells computer - yo, it's done.

6. Computer lights funky 4X4 light in dash, probably over CANBUS.

 

Solved the problem. 4x4 actuator contacts were barely making contact, little bit of solder and its working like a champ again. This is why it would work sometimes, not because of the locker.
Here is a link to the fix in case anyone else runs into this https://www.tacomaworld.com/threads/how-to-trouble-shoot-4x4-actuator.263525/#post-6450282

And no Toyota didn't help me at all. My installer did.

 

Glad you got that sorted out!

SO the factory "booger welds" were just shit?

 

They don't even have welds they just make continuity by touching..... Smart engineering.