Interesting how their method of dealing with this issue completely changed when you asked for the old module back. We're they even replacing it in the first place..

Actually they said they can’t provide the old module if it’s replaced under warranty. They claimed that they had to send the old module to Toyota. I’m gonna replace the module myself and put my own breather…if this solves the issue, I’ll be beyond thrilled. The dealer’s master tech said this is the second truck in his career that he’s seen the ADD fail. I just can’t understand how the breather line could have been ruptured. Especially by a lift (possibly by diff drop?). Part of me thinks they might have faked it? Idk.

Here’s what official record says:

)Z-DIAG
DIAGNOSIS
TECH(S): 158
CUSTOMER STATES MODE CHANGE MALFUNCITON WARNING ON REPLACED
CONFIRMED 4L0 LIGHT IS FLASHING, AND MODE SELECTION LIGHT
IS FLASHING. RAISED VEHICLE,
AND INSPECTED. WITH SIFTER IN
4WD THE FRONT DRIVE SHAFT IS SPINNING, BUT NOT THE FRONT
WHEELS. MANUALLY POWERED UP THE FRONT ADD ACTUATOR, AND
CONFIRMED THE FRONT WHEELS ARE NOW SPINNING. CHECKED FRONT
ADD ACTUATOR DL1, AND DL2 AT 4WD ECU WITH SHIFTER IN 2HI.
. BOTH HAVE 12 VOLTS. CREATED TAS CASE,
CASE NUMBER 221370093.
WAS INSTRUCTED TO INSPECT THE VENT HOSE FOR CRACKS OR TEARS.
CONFIRMED VENT HOSE IS TORN, AND IS ALLOWING CONTAMINANTS TO
ENTER THE FRONT DIFFERENTIAL ACTUATOR. RECOMMEND REPLACING
THE FRONT DIFFERENTIAL ACTUATOR, VENT HOSE, AND RECHECK FOR
PROPER OPERATION.
NO CHARGE FOR DIAGNOSTIC ONE TIME GOODWILL.

The frustrating thing about warranty work is that it sometimes doesn’t make sense. It’s very scripted with thousands of combinations of “if this, then that.” Unfortunately sometimes the logic doesn’t add up, but the response has been predetermined by the OEM, so even if there is an alternative method or fix, the dealer can’t go with it because it’s not approved.


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I'm sorry to hear that.. only thing I can think of is the line got pinched somehow, but I'm not sure how? But that breather line allowing moisture into the ADD makes some sense, though I'm not sure how fast that corrosion would set in (though all you'd need is the limit switch to act up to cause problems). You can jump the motor pins and/or de-pin the limit switch to "trick" the vehicle, useful for diagnosis. As for the front wheels not spinning, that is because the front differential is open; when the ADD isn't engaged, the path of least resistance is through the disconnected axle shaft.

Unfortunately when it comes to warranty work, parts have to be returned to Toyota; it's just how warranty policy works.

Hopefully this will be the last one you need to replace!

Yes. Thanks! I started doing more research on the actuator flooding, and it appears pretty common.

Front 4wd actuator POS | Tacoma World

Some guy even went ahead and removed the entire actuator assembly (nifty idea, but then the front diff would be spinning, no?) curious if this would cause wear:

How to: Deleting ADD system | Tacoma World

For now, I ordered the new ADD and will install it myself. I am planning to use Ultra Black as a gasket maker. And then I think I’ll just plug an ARB breather line directly to ADD, skipping the factory breather line that ruptured. The factory line is tucked away so deep against the engine that it’s no surprise that the tech couldn’t identify it as a problem. You just can’t see it unless you pull it out, and why would you pull it out? It still doesn’t make sense to me that a lift would affect it (though I can see the diff drop possibly do the deed, as it tilts the diff and pulls on the breather line, which is pretty tight against a metal line).

Overall, the dealer was very nice to me (assuming they didn’t lie). Spent a lot of time talking to the tech, and even waived the diagnostic charge (albeit after some haggling). The tech showed me the 4wd testing diagrams that you guys were talking about. He popped open the glovebox compartment to access the 4wd circuit).

If anyone has any additional tips or suggestions on replacing the ADD and breather hose, please let me know.

I hope this was your issue! I'm not going to get excited yet though. Your *diff oil and magnets* could be the one to tell you if the breather hose was actually sucking in moisture and debris or not. Be very observant of things like this. They hold valuable clues and answers. I think there is a check valve on that breather that can get stuck too. I'd have to check it out though, I'm not sure. And whether that hole is before or after the check valve.. May be something you want to look into in more detail

I think the diff fluid should be fine unless the seal has failed. The breather hose that’s ruptured leads to the ADD motor. The front diff breather is fine. Very odd, considering the two hoses are attached to each other. But yeah, I’ll take a look at the diff oil

Guys, quick question. Got the new actuator. But the shift fork on the new one is currently in 4wd position, so I can’t mate it to the current 2wd position. I understand I can just connect the actuator to the batter and switch, right? How do I do it?

I figured out how to make the motor run. Connect the bottom two pins to the battery and voila.

Also, I removed and replaced the ADD. The old one actually worked as far as engaging 4x4. But when I cracked it open, it was full of water and corrosion. See pics.

Also, I’m not the only one with this issue. This guy found the culprit: there’s a hose clamp that punctured the breather. Tacoma A.D.D. Diagnostics (4x4 Front Differential Actuator) 3rd Gen 2020 - YouTube

Attached Images

   

Ah... sorry, a bit late to the response. Just plug the ADD into the factory harness and set the vehicle to 2WD.

You don't need it to be installed to make it work (we have like one or two ADDs we scavenged off old front diffs in the shop that we use to verify the circuits).

As for the hose clamp tearing a hole in the breather hose. I wonder if that's from installing the diff drop or just poor factory hose routing? It wouldn't surprise me if the diff drop stretched the hose enough that it could be eroded by the clamp, but it also wouldn't surprise me if it was poor routing to begin with. Those breather lines are a bit close to the power steering lines.

Thanks, yeah, I think the breather line locations aren’t great. Right next to the engine. I’ve been concerned about the front diff breather that the ADD breather was clipped to, but there wasn’t any water in the diff. I do think that the diff drop kit likely pulled the breather line into the front diff hose clamp, which killed it over time.

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.

Enjoy your proper 4wd!! Go hard and let's hear a new reliability review !

Thanks! It’s worked flawlessly over a dozen times now as I’m breaking in the gears.
Also, wanted to follow through on the new breather hose. I used ARB from the mount in the engine bay, put it under the battery, around the radiator, and down attached to the upper portion of the sway bar. For the last bit, I used 1/4 to 1/4 barb connector to attach the stock rubber hose that comes with ADD to the ARB breather hose. Has been great but no water crossings just yet haha.