Also, wanted to share my story further.
After leaving the dealer, I ordered a new ADD module. It’s generally around $300 for the OEM unit (of course, dealer wanted $600 for it). As a side note, I highly recommend getting the OEM unit over Chinese stuff, like Dorman. While the latter costs $70 rather than $300, you can clearly see play in the shift fork - where there shouldn’t be any. Not a good sign, just saying.
When I got the actuator it was in the 4x4 mode, as I said earlier. The trick to run it is very simple - connect the bottom two pins to negative and positive terminal to make it go one way, and reverse to make it go back. I then removed the stock ADD. It was quite a PITA because one of the 4 bolts is extremely difficult to access. I ended up removing the front two diff bolts, dropping the diff, and using two extensions to reach the top two bolts.
Then I got the new ADD and put some Permatex Ultra Black gasket maker on it. It was my first time making a gasket, so i can’t say I’m confident in my seal. Putting the ADD back was a bit tricky because the sleeve connecting the axle to the diff slides very easily. The shift fork moved it aside when I was installing it, so I took it out and worked to fit the shift fork over the grooved sleeve. After I put it on, you’re supposed to wait for 1hr before you can torque the ADD bolts. I was impatient, so I started the truck to see if the error cleared. I could hear the ADD motor shift and the blinking 4L sign disappeared. However, multi-terrain select was still blinking and it still said 2WD to 4WD Shift Malfunction. So I though that I probably installed the ADD shift fork to the side of the sleeve and it didn’t engage correctly. Being paranoid, I went back, and took the ADD off again. Noticing that my gasket was not very impressive, I added a bunch more Ultra Black. (Taking a step back, Toyota uses red silicon which dries completely in 1hr as opposed to 24 hours with Permatex; it is 5x the price though). I then put the ADD back, this time being extra careful with the sleeve location. Put the bolts in, and checked again. Still those failure lights.
So I disconnected the battery, thinking that the system needs to restart itself. After waiting for some time, I re-connected the battery, and….the lights were still there and 4x4 would not engage. At this point my heart dropped and thought I was an idiot for not paying the dealer $1400 to fix it and be done with it. Some really gloomy moment there. At this point I started thinking if I can just force the ADD into 4wd and leave it there. So i put the truck into 4low, then I took a battery jumper pack, attached some tiny cables and connected them to ADD pins, forcing ADD to go into 4x4. Then I connected the factory wires back. When I started the truck, to my great surprise, all the 4x4 errors were gone, and the truck went in and out of 4lo. Thinking back, I remembered the Car Care Nut’s YouTube video on Toyota 4wd, where he said that the ADD can go into limbo if the fork is in the position between 4wd and 2wd or something like that. I believe the ADD was likely in that limbo when I connected it to the truck and that’s why it didn’t work at first. After waiting 24 hours, I put oil into the front diff and took it for a spin. 4wd worked as did all the related systems, with no lights on the dash. Thank God!
The only thing left to finish is to mate the ARB breather hose to the actuator nipple. The ARB hose is about 3/16 of an inch while the original rubber hose was about 1/8. I’m still looking for a solution here. I wasn’t able to find hose clamps that would fit, but also the ADD line is fairly hard, so it might not clamp. Thinking of maybe using some silicon adhesive, but still TBD (please share your ideas). I also put the breather hose far away front the engine, unlike the factory breather, guiding it under the battery and along the KDSS mount. My experience with factory breather hoses made me worried.
That’s it for now. Will report back after some time passes.
