Well, the story continues. Had a productive day wheeling. The 4runner 4wd system worked great. Except when we got back to pavement, a *new* error showed up: 2WD to 4WD Shift Malfunction. Came up randomly while I was driving on the street in 2H. Naturally, 4wd did not engage with that code, and the 4x4 green blinker didn’t show up. Luckily, the 4wd circuit appears to restart every time I start my truck (can hear a distinctive click and clears old 4x4 codes - this started happening after whacking the ADD). So, the error went away. Only to come back the next time I drove it. Again, restarted the truck, no error, 4H and 4L engage fine. Now this is very weird (and sketchy). I’m feeling more of the need to have the dealer see it yet again, though I’m not sure what they can do if the code doesn’t persist. Ideas?

Sorry to hear. In my experience mechanical issues are very rarely intermittent. This almost has to be some sort of electrical issue. With the amount of off-roading you do your harnesses, grounds, and so on have likely seen a lot of water, mud, foreign debris, and potentially even some contact/abrasion.

I would definitely take it back to the dealer.

Thanks. The truck barely goes off-road 4-6 times a year. Not even a weekend warrior status, yet so many issues. I just don’t think this is what I signed up for when I bought a Toyota for it’s reliability. It seems to have just as many issues as a Jeep or Land Rover have, they just aren’t as critical.

This click under the passenger dash doesn't sound like a relay engaging or disengaging by chance? Or a mechanical metal on metal clank? Checking that circuit kind of sucks too so maybe it's best if you just keep taking it to the dealer.. they need to do a more thorough diagnosistic though and provide you with the results.. it's b_llshit you haven't been able to use your 60 grand truck fully functional in so long. Like I mentioned a long time ago on here you can test the actual add module/motor by back probing at the connected add connector, connected to a power source and proper relay. This is in the FSM so the technician should do this f_ckin diagnostic shouldn't he before replacing the module.. I'd be getting irritated. Hope all turns out well.

If you can duplicate the issue consistently, then show it to the service writer/technician; that will be enough for them to follow it diagnostically. As long as the technician can make it fail, they can go from there even if it "resets" from cycling the key, the more detail the better (I would rather have too much information regarding how to duplicate a weird issue than not enough; makes it easier to filter out what is relevant vs. what is superfluous).

As @Jakeepoo3 stated, if you're hearing a click under the passenger side dash, that might be the 4WD module itself. It does have a couple relays/high amp switches in it for the 4WD system functions, it should have been tested before being replaced. I know the earlier 4th gens had a warning in the FSM to not turn the vehicle on with certain things disconnected as it could cause damage to the module or the actuators; can't recall if the 5th gens have that?

I would at this point take it back to the dealer and have a civil chat with the service manager about the issue, maybe even touch base with Toyota's corporate side to cover your bases. This will likely get a TAS Case (if it doesn't already) and should have FTS involvement if not Tier 2 since this would be like the 2nd/3rd failure in a row for the same issue, so theoretically you shouldn't get too much crap/push back from the dealer or Toyota (at least, in theory...) I am really curious what the issue will end up being... this one seems very interesting.

Thanks. Yes, I think I’ll have to take it to the dealer. The 2WD - 4WD Mode Change Malfunction came up a few more times. Each time when I took a hard left turn at speed (in 2wd on the street). It’s not perfectly replicatable, it happens only so often. The malfunction is recorded in the vehicle alert history though.

Are you guys saying that the culprit is likely the 4x4 ECU and it just shows itself through the ADD? The click under the passenger seat each time I start the car is the same click that I hear when 4wd engages.

I'm saying it's a unique issue and I haven't run into it... at this point without having your vehicle at my shop to do the testing myself and relay that to maybe TAS or my FTS... I can't really say where the original issue is unfortunately, all I can do is speculate based on "heresay" from you and the dealership and hope that my diagnostic intuition is correct. :/

Sounds like a relay when you say click and makes sense it would do this at restarting the vehicle after a malfunction. Engaging 4wd doesn't make a click that I have ever noticed.. The f_uckin module works properly I guarantee 95%, just intermittently, so it's not the issue partner. It's in the circuit somewhere.. try to get it to f_ck up for them on the way to the shop so they can plug it into techstream drive it and read live stream data.. Anyways give all these details SUPER specific to the technician and his BOSS.. go in there knowing what the f_ck you're talking about so they can't circle jerk you around the fourth time. Going around a corner sharply deactivating your skid ECU is a symptom of improper zero point calibration. That's exactly what happened to me after 3" lift.. Be sweet and cute like blackworks said or they'll just keep f_cking you around. Request the proper diagnostics and results. THEY SHOULD BE TESTING FOR CONTINUITY AND PROPER VOTALGE SIGNAL/VALUES UPON SWITCHING BETWEEN 2 AND 4WD WITHIN THE CIRCUIT. THIS DIAGNOSTIC IS CONDUCTED BETWEEN THE A.D.D. CONNECTOR AND 4WD ECU.. Request these circuit tests and proper functionality in the circuit printed out with values included to ensure they actually did their job without being an as$hole. If they try to replace the module again request they perform the DIAGNOSTIC I'M ATTACHING for you also at the bottom to determine if it works properly before repeating this dild0 cycle. Also I'm attaching the circuit testing values they need to provide you with, the values may not be the same but the same principles apply upon switching to and from 2wd, 4wd. This is where I have issues and tell them to get f_cked and proceed on my own. I do this sh!t all myself having a 2010 with no warranty, scannerdanner style with nothing but a test light. I can vouch that Toyota 4wd is f_cking amazing after 100,000 miles of mostly foresting adrenaline junkie style, hard!, even without the skid functions if you know how to drive, she'll beast right through!. Don't get discouraged and make them get this resolved. These modules all linked together are the problem, Toyota engineers need to simplify communication and make each module readable for input DTC codes instead of following a dufass flow chart that says replace module for every code. Durp.

Give me a little bit I'm going to find and attach diagnostic information you need to understand and request from these f_cks before you go in there. KNOW YOUR Sh1t!!

Based on him giving specific details and requesting proper diagnostics as I mentioned before... Hopefully they can do a proper diagnosis. I'm going to attach the information he should be getting from a dealership technician

Thank you! I appreciate you feeling my pain. I’ve honestly been so discouraged with the repeated 4x4 issues that I’ve been looking at other vehicles.


Yeah, I also feel very strange seeing all this stuff pop up yet also seeing guys take Toyotas through the Road of Bones and the Artic circle without issues. Do you mind describing the issues that you had after your 3” lift that you mentioned? I did have zero point calibration done by an alignment shop. I’m just trying to figure out the best way to approach it. The code is thrown intermittently and then goes away when the truck restarts, so chances are I won’t be able to replicate before dealer except by pure luck. But I was thinking of raising the issue of 4x4 not engaging (blinking 4x4) and going away and then showing the current issue to the dealer. Maybe they can use tech stream to read the codes. My truck’s issues have only been handled by the master mechanic at my local dealer. And I’ve spoken to the man. He told me that the ADD failure is very rare in his experience. The Car Care Nut (YouTube channel, also Toyota master mechanic) confirmed that ADD is generally very reliable. This leads back to me thinking that the ECU is likely the culprit.

Also, forgot to mention. When I get the intermittent 2WD 4WD Mode Malfunction, also the Multi Terrain Select fails and blinks. And there’s a blinking 4L. When putting the transfer case into 4H or 4L the green 4x4 light doesn’t even blink.

Right this confirms that there is communication error between ADD and skid ECU. Remember the circuit?? ADD module is a skid ECU input. You're skid/abs functions such as MTS will be disabled but 4wd is still functional when the skid ECU can't receive ADD module signal. Make sure to relay this symptom to the flow chart following, wannabe tech. My issue was caused because I neglected to zero point calibrate immediately after lift. Yaw/g spot 😝 sensor detects lean in cornering and acceleration/de acceleration. A little 3" lift is enough elevation change to make that g spot go crazy! (EBD) You should have seen the codes I got 😂! The whole brake booster assembly, accumulator, and master cylinder "needed replaced" after this nearly killed a grandma off a simple sensor signal malfunction. The point is major codes come from little issues 90%

Here are the diagnostics that shall be done to test the module/motor itself. The other sheet is the diagnostic to test the circuit between ADD, 4wd ECU, and skid ECU communication. Get yourself familiar with this information and understand the processes. The technician can't bullsh1t facts and knowledge 🙏

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Last post look about right blackworks.. I can't deal with f_ck tards without getting worked up so it may be beneficial for you being a Toyota guy to give this gentleman some tips on how to deal with these Toyota tricks. Without him pissing them off and getting the these diagnostics done and confirmed properly. This gentleman doesn't deserve this sh1t. Make the f_cker drive it until it malfunctions hooked to techstream. Who cares it's just a break for him. Have you ever disabled all your VSC, trac functions completely after starting truck before the problem occurs? Does this malfunction only occur when you're skid ECU is activated. How does it act if you disable the skid ECU after start up. Ever malfunction with skid disabled?? I'm rooting for you bro!