A.D.D. actuator not moving, even when outside of diff.

Hi all, like many I had my 4x4 go out. Read through the forums and watched some videos and decided the place to start was the ADD actuator on the front diff.

Took off the original ADD (yes, it's a real mother to get to the top 2 bolts), popped open the plastic case, and a ton of muddy water poured out. Ok, so there's my problem, easy peasy.

Thought it seemed beyond cleaning so ordered a new ADD (2nd unit) and popped it on and ... nothing. Still no 4x4. No clicking sounds when trying to switch. Green 4x4 light and 4Lo light blink in unison as soon as truck is turned on.

Hmm, not sure what do do now. I ordered the ADD off Amazon, so not a toyota part. Same part that was recommended via a link in one of the youtube vidoes of someone swapping an ADD that water infiltrated.

My next thought was maybe that amazon/chinese ADD was bad? Well I don't want to have to open the diff and deal with the diff oil again until I know what is going on. So I ordered another one (3rd unit) figuring I can test it and return it if not needed. This time, I decided to hook up the 3rd ADD (to the electric plug by itself to see if the arm would move when switching from 2wd to 4wd. Nope. Doesnt work. No click, no change in flashing, and definitely no movement in the ADD's arm. Tried disconnecting and reconnecting the battery to see if that fixed it but also nope.

A little bit stumped now and not sure what do check next. I suppose it's possible both the 2nd and 3rd ADDs are faulty out of the box but sure seems unlikely.

I guess I could theoretically bench test the 3rd ADD but I don't know how. Any insight would be appreciated!!

I own a multimeter but have only used it once and am kind of intimidated by anything electrical.

Seems like the ECU might be the next place to check but not really sure what to do.

One other note: the truck has been in 2wd, not 4hi since this ordeal started. When I installed the 2nd ADD the arm was definitely lined up correctly on the little collar (to passenger side).

Sorry for the novel but would really appreciate any help. I talked to a garage near me and they quoted several hundred just to diagnose, don't even want to think about what the stealership would charge.

 

Get you a backprobe, a sewing needle, or small T-Pin and check your limit switch voltages as outlined in the thread below.

Post your results and we can see where we need to start looking.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

Thanks for the help. I just read the first 20 pages of that thread and have a lot better handle on what I need to do.

 

This primarily applies to 3rd gens, but its easy enough that you MIGHT try it first. (no guarantee it will work)
(Especially aftermarket) replacement ADDs seem to often be shipped with the actuator run too far one way or the other, such that the ADD has been moved past the position sensors (traces) valid positions. I recommend putting the ADD into a mid position to start with, it doesnt seem to generally matter if its in 2hi or 4hi, just any mid position will do. The ECU will move it where it needs to go as long as its a valid position.

Recommend using ~4v-6v or so across pins 1-2 momentarily to position to middle position, if you have polarity wrong, just reverse...

 

Interesting, didn't think that was possible but it certainly wouldn't be too surprising with the level of quality control of parts anymore.

 

An update just because I know its frustrating to find threads that don't share how things ended up...
I think the actuator on the transfer case was also waterlogged. I replaced that too, which is a much easier swap than the front diff actuator (seriously took me less than 10 minutes to swap the tcase actuator and I'm really not that handy), and now everything works great!
The part was only about $100 on Amazon. Didn't crack open the old one, but I wouldn't be surprised if I could have dried it out, cleaned it up, and reused it.
I think the Culprit was the vent hose on the tcase - it was cracked and there is mud on the plastic nipple...
Still not sure how the front diff actuator got so much water in it because the hose on it seems fine and it wasn't cracked or anything...

 

Someone else had this issue and found a hole rubbed in the vent line further up from the ADD.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/page-17#post-28163684

 

I assume you left the shift rod in the transfer case
How did you time the new actuator to the transfer case?