Transfer case actuator questions

Hello Everyone. I recently experienced some problems with the 4x4 controls on my 2008 base model Taco. Truck would get stuck in 4 high with dash lights flashing 4 low and I'd have to use a spare pigtail with a 9 volt battery to move the ADD and TC actuator back into 2wd mode. I later discovered that a few taps on the actuator with a hammer while the truck is running will cause it to move into position also. So I ended up replacing the transfer case actuator and the first two tests it still got stuck in 4H while flashing 4Lo. Bummer huh? We've all been there and it's often frustrating.
2nd time it stuck I tapped on the actuator with a hammer and it moved into position but to my surprise it started working fine after the tap-tap. I moved it in and out of all modes 8 or 9 times and no sticking in 4H.
But I'm still wondering why the new actuator initially stuck?? It's working now so should I leave well enough alone or is there anything I should investigate?

This 4x4 issue got me thinking about ways to simplify the system. Delete the ADD would be the first step but I'm also interested in bypassing the 4x4 ECU and just rigging up a button and reverse polarity switch to move the actuator into position. I could wire the 4H and 4L sensors directly to some indicator lights so I would know when the shift rod is in proper position. I would leave all the factory wiring in place and run my own harness. Does all this sound feasible?

I'm wondering if anyone has the part numbers for the 4H and 4Lo sensor pigtails that plug into the TC actuator? I think they're both 2 pin connectors. I already have the 6 pin connector.
Thanks for reading my post.

 

Your idea sounds feasible. Shouldn’t need any pigtails all the splicing can be done right behind the glovebox and you can leave the wiring at the transfer case alone.

 

I tested my 4wd controls again this morning and it stuck in 4wd high with dash lights flashing 4Lo. Tapping on the actuator did nothing this time. I used my 9 volt battery pigtail and moved the ADD into 2wd mode. Then I started the truck with the switch in 2wd position and the TC actuator moved back into 2wd mode. Then I tested the 4wd controls again and it worked fine. I'm thinking my ADD might be the problem. I already have a spare one so I'll replace that next. I'm really just guessing at this point. My ADD is not original and the person who replaced it never connected the breather hose. They just left the short plugged section of hose that comes with the ADD and left the breather hose dangling. Could lack of ventilation effect the function or shorten the life of the ADD?

The main reason I wanted extra pigtails is so I can experiment with a spare actuator that I have and make sure my ECU bypass idea works before I start cutting factory wiring. Where do I obtain a schematic of the 4wd system? That would help me sort things out.

Question: Does the harness that plugs into the transfer case actuator run directly to the 4x4 ECU? So I just find the same color wire going into the ECU? I appreciate your time.

 

You probably have a limit switch that isn't making proper contact or the actuator wasn't properly timed when it was installed.
We have a thread with just about everything you could want to know about the electrical side of the 4wd system, we can even help you diagnose it should you want to.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

the vent hose being disconnected can allow moisture to get in and corrode the contacts shortening their life yes.

there’s a thread on here for how to test the limits, @Dm93 has the link.

the colors may or may not be the same color. The schematic should be on that link, the wire colors changed in 2009 so make sure you have the correct year schematic.

 

I timed the new actuator by moving it into 2wd position on the bench using my 9 volt battery pigtail as described above. The truck was in 2wd when I parked it and I made sure the shift rod didn't move when I slipped the old actuator off and slipped the new one on. I confirmed the actuator position by hooking up a meter to appropriate terminals and checked continuity.

I did replace my ADD today and it hasn't stuck once since with 8 or so tests in and out of all modes. I'm thinking that my ADD had ADD. It couldn't remain focused long enough to complete it's task and it possibly wasn't sending proper feedback to the ECU. I apologize for my lack of technical knowledge with electronics. My main mechanical experience is with classic Chevy small blocks and 80's diesel Mercedes. No complicated electronics aside from the Mercedes climate control. The Taco is an unfamiliar animal to me but I'm learning. Thanks to all for the helpful advice.

 

It's not really any more complicated than any other ESOF 4wd system, the difficulty arises in diagnosing it due to being unable to talk to it with a scan tool to see inputs, outputs, and trouble codes so you have to test voltages at the module to see what it's "seeing".
Once you know the sequence of operation and what to expect it makes diagnosing it much easier, that's why I took a deep dive into reverse engineering how the system works so I could try to help people actually diagnose the system instead of throwing parts at it. For the most part we've been pretty successful in diagnosing it using limit switch voltages.

 

Thx for the input. After replacing the ADD it's working fine. I'll test again tomorrow AM when it's cold but if the system is working properly I'll leave well enough alone.
I'll definitely look you up if any problems emerge that I can't diagnose. I do miss the old manual transfer case and manual locking hubs.

 

You can swap in a manual tcase and delete the ADD

 

I have definitely considered the manual transfer case swap option. Can you direct me to any good information on that subject? I've seen some sporadic information but I'd like to see an actual documentation of a successful swap with some specific steps. Thanks for reading my post.

 

https://www.tacomaworld.com/threads/lets-see-your-fj-case-swap.455278/