How are you actuating the ADD? The FSM seems to make note that failure to utilize a relay can cause damage if you're applying direct current to the ADD to test it? (Not entirely sure what they're reasoning is just glancing at it.)

Those resistance values don't make any sense to be to be honest, nor do I entirely care about the motor's resistance value at the moment as A.) it seems to be operating so... yeah B.) this doesn't sound like a motor issue as much as a driver issue (meaning that whatever processes are required to be completed/passed before the motor is commanded on have failed.)

Pins 1 & 2 (DM1 & DM2 respectively) are specifically for the motor operation. Pins 3~6 (ADD, GND, DL1, and DL2 respectively) are for the limit switch and ADD Detection switch. There should be no continuity between any of Pins 3~6 to Pins 1 and/or 2 as they are not physically wired together in the ADD according to the EWD (electrical wiring diagram.)

I'll try and reread your post tomorrow if I have some free time, as I could be interpreting your text wrong at this late an hour... but can you maybe post pictures of your testing set-up (and what pins you're checking) as well as what diagnostic steps you've taken and where you're getting your reference values (i.e. I don't understand why you're checking Pins 1 & 3 for continuity to begin with; did you find a forum post referencing that or a page in the FSM?)

Because at the current moment I'm a bit lost as to how you arrived at the issue being in the ADD and what diagnostic criteria you're using; so getting an idea of your diagnostic steps will help me (and the forum) better follow your logic here.

Yep, it is hard to read a long post....

Let me summarize...
He was totally guessing about the ADD...

The symptoms were...no 4wd operation (no 4wd lights blinking or anything on the dash). However, it sounded like the TCASE was engaging the front drive shaft and allowing the reduction gear for 4L.

But still no ADD, and therefore no actual 4WD up front, just spinning the diff with all power going to the disconnected passenger output shaft.

The lack of any lights on the dash led several of us to conclude something with the 4wd ECU controls and probably no motor control to the ADD. My guess was the 4wd indicator switch in the T-Case.

Should be easy to test that if you can get at the connector. If not, I would assume there is some guide to the pins on the 4wd ECU.

This may just end up being one of those dealer visit is the only way scenarios. Can't expect blackworks or anyone else to work for free LOL, but I like these threads because they are educational for everyone. We all may have the same issue at some point....

I understand how he arrived at suspecting the ADD component of the system, I have no issue with that as it's pretty cut and dry. What I didn't understand in his diagnostic steps is why he went from "I think there's an issue with the ADD part of the 4WD system" to "I have it apart on my bench and I'm testing one terminal for the motor (Pin 1) with one terminal for an unrelated ADD sensing circuit (Pin 3)"

Additionally his results, combined with his manual activation of the ADD (again, not entirely sure how he's achieving this; i.e. is he using just jumper leads off the 12v battery or a relay, or do you have a 12v power supply? ect.) make no sense. He should have some resistance value between Pins 1 & 2 (the power & ground supply for the motor operation), if he's getting an "OL" or Open reading then the motor should not function when manually jumped. I also don't understand why he's testing between Pin 1 & Pin 3 of the ADD, because those are two entirely separate circuits in the unit itself; so he should get no continuity between them (Pin 3 is input voltage for the ADD Detection Switch, which grounds through Pin 4).

So to make sense of his results and where he is in his diagnostics with what logic/information sources he's using. Otherwise we have to start from the very beginning and throw out the information because based on the way the FSM details the diagnostic procedure, he's way off base and ignore everything he's done after "I think the issue is in the ADD part of the system." I'm not entirely sure is that makes any sense?

Post Note-
I'd post pictures of the EWD and the sections in the FSM if I could; but after 2005 model year being able to save any files from TIS is difficult.

I see the cause of confusion and apologize for my lack of detail.

I'll attempt to make sense of it. I was unable to locate proper troubleshooting material other than what I found on forums and YouTube. I was steered towards the ADD by comparing my issues with those found in other threads. I completely missed the tcase switches and jumped right for the ADD. A video I watched of an FJ ADD repair had instructions to ohm out pins 1 and 2. Pin 1 being the top most pin when the ADD is installed.

I tested the connection between 1&2 when the ADD was still attached and my multimeter showed a 1 when set to measure 20 ohms, this is what is displayed on an open circuit. It's a cheap Craftsman model.
My function test consisted of leads ran directly of the vehicles battery. Positive to pin 1 and ground to 2, the motor functioned. I then reassembled the ADD and tested it directly from the battery again with the same results.
Pins 1&3 were tested just to see what Id get as I expected them to read 1 as well. I included the information in case it led to something.
Based on @wfo9 posts, I reinstalled the ADD and tested the tcase switch, passenger side switch, with tcase in 4-hi reads a 1 or "open". I've ordered a replacement from Toyota and will try and figure out how to remove it tomorrow.

I clearly am not a mechanic, forgive me for my less than technically accurate writing. I am an EOD technician (bomb tech) by trade and haven't had the opportunity to work on vehicles since before 9/11.
Thanks again for all of your help, I know nobody wants to work for free. @BlackWorksInc and @wfo9 , I will buy you a case of beer or make a donation to a charity of your choice.

It's not a problem and please don't feel bad about it, I don't expect everyone to be able to recite technical information like it's their hobby (unlike me some people actually have a life). As long as you can convey the information in a way that I or other members can somewhat follow you on (I like pictures! ), then we can do our best to help; lots of members come on the forum and will post "I have a weird noise, help me" and not realize that diagnostics don't work that way. We need information such as "what is the noise? when does it happen? What are you/the vehicle doing when it happens? ect." so part of helping you is better understanding the problem and the step you took/will take to figure it out.

I had a feeling that your continuity check of Pin 1 & 3 was just to check for reference/internal short on isolated circuits (which I would probably do as well if I felt inclined), but without any context in your post I wasn't sure if you were following some diagnostic chart/thread post or just doing it to check for some internal shorting.

In regards to checking the Transfer Case switches, you're talking about these?


The "Transfer Case Indicator Switch (Neutral Position)" is the second switch on the driver's side of the transfer case and should read below 1Ω when the transfer case is in the "Neutral" position and read 100kΩ or Higher when it is out of "Neutral." (in this case what Toyota is saying is that if the resistance is anywhere between 100kΩ and "OL" or "Over Limit" which is a common way of saying Open in DMM speak, the switch is fine electrically)

The "Transfer Case Indicator Switch (4WD Position)" located on the passenger side of the transfer case should also read below 1Ω when depressed (this time when the transfer case is in either of the 4WD positions) and 100kΩ or higher when it is in 2WD.

The 3rd switch is for 4Lo and is in front of the Neutral switch, it should read the same 1Ω or lower when the case is in 4Lo and 100kΩ or higher when it is in any other position.

Post Note-

How ironic you're an EOD I wanted to be a USMC EOD a while back but got turned down due to some BS reasons I decided not to fight them on; anyways, being an EOD I'm sure you're very familiar with a DMM, but you may want to check out this thread: The Toolbox and How to Use It it's got some good information for members who want to learn how to work on their vehicles a bit more. Particularly useful if you want to brush up on automotive technical junk if it's been a while since you wrenched.

The only thing I will add right now is "It is sometimes better to ask questions first."
There is a lot of good information here and on youtube. Unfortunately there is a lot of bad information too. This thread has some really good information. Good luck and report back!

No reason to apologize... your way ahead of the game compared to most... I only brought up taking it to the dealer.. because there are many situations these days that just can't be resolved without all the proprietary diagnostic tools and guides + hands on access to the vehicle.

Sounds like you may have found the issue. If I read everything correctly... the switch seems to be bad. I would tipple check it before diving in...(compare with the other two....)

Like I said before, the repair manual (which is available for download here TIS FSM for 2010 4Runner is here...) says to remove the transmission and Tcase as a first step to replace it, but that may not be required. There is often a better way.... I would go look at mine, but I have skids in the way that would be a pain to remove...

Keep us posted.

I know this isn't really related to the OP's issue, but if you have the screen up of the wiring diagram, and you're on a windows-based pc, you can hold ALT and press PRINTSCREEN to get a screen cap. open whatever photo program you have (MS paint would even work here, or photoshop or ) and CTRL + V to paste the screen shot.

You can then save it as a jpeg and post it up!

There is actually an easier way on recent versions. From vista on up there is a tool included called the snipping tool. It lets you capture screen, free form, rectangle... highlight draw... and save as jpg..... super easy and convenient.

If you can't get the switch out on the car, the transfer case can be dropped without removing the transmission. There's seals between the two so no fluid should leak out.

I don't know if we can be sure it's the switch. It sounds like the OP is basing the diagnosis on the fact that the front driveshaft locks, but the switch still reads open. But is it possible that it could be partially engaged, enough to lock the front shaft but not enough to trigger the switch?

This thread is a great resource. Over in the 4th gen section people typically bang on the t-case actuator with a hammer and/or loosen some bolts to try to get it to work. But those usually fail due to water getting in or old age. The ADD rarely seems to be a problem, or maybe everyone just ignores it.

I doubt what you described is possible. There is no actuator. The 2010-2012 sr5 trucks have a manual shifter moving the shift forks mechanically (same as all the trail editions 2010-2016). Only the 2013-2016 sr5s have an 4wd actuator motor. All the part time 4wd models have the same ADD actuator. It does fail, seen it happen to an FJ.

Also, that is why I thought it would be a good idea to test the other switches.... N and Lo. It would also be possible to rig up a manual switch or just close the circuit manually for testing 4wd function. These transfer cases are really simple and there is not much that can go wrong that is not mechanical. On 2012 and earlier, the switches are the only electronics in them.

That would be much easier and could be done pretty easy on jack stands. I've never really looked at what it would take, but there seems to be a decent amount of room to work in. But sometimes there is that one bolt.....

I hate when repair manuals give a labor intensive solution when there is another way...They are rarely ever efficiently written.

The banging on the transfercase solution has to do with the fact that the actuators on our 4th gens tend to get sticky/seize up from lack of use and/or other conditions (such as water intrusion). Most of the time tapping on the case while shifting will break loose the crud on the shafts and let it move in and out. The ADD doesn't go bad too often on the V6's from what I have seen.

In this particular case, since the OP has a VF2A Transfer Case unlike the VF4AM & VF4BM units found in the 4th gens, it's manually actuated with a physical shift lever. Yet, while the transfer case is manually actuated, they still use an ADD to actually engage the front axle.

Alright gentlemen, I believe we have solved the issue! After an evening reassembling the ADD and installing it I sought a way to remove the switch without dropping the tranny and tcase. A replacement transfer case indicator switch was on order from my local Toyota dealer, to the tune of $84.00.
Today I searched my small town for a 27mm crows foot wrench to remove the switch, there is almost no room between the top of the Tcase and the tunnel walls. To no avail, not a single store carries crows foot wrenches bigger than 20mm. I was able to borrow one from a local mechanic!! This was awesome, he let me borrow the tool, gave me some tips, and wouldn't take any money. I offered my phone number and drivers license as collateral and went back to my garage.
I was able to crack the switch loose with a 1 1/16" crows foot 1/2" drive attached to a 1/2" drive ratchet. Once cracked loose, it was finger tight. The replacement was installed, tighten with a 1/4 turn on the crows foot. I returned the tools along with a case of Miller Light ( I had seen one sitting on his work bench) and he was very grateful.

I tested the system on the way to his shop, 4-hi activated in drive at 20-30mph. The dash light blinked once and locked on. I then tested 4-lo and was not able to achieve activation with the transmission in N and the brake applied.

An hour later I drove the runner 10-15 miles and tried activating 4-lo again in my driveway. It was a bit slow and I had to roll backwards a few feet in neutral before it activated, but so far all seems to be operating as designed!!
All that said, you all were a big help and thanks for not flaming me out of here.

If I have not addressed something you have questions about, feel free to ask.
I was also able to install cat-back Borla exhaust and a TRD cold air intake over the last two days. A Toytech 3" lift is on the way, should arrive Monday!

Top picture is the switch I replaced, passenger side. Tight as hell to get to, but not impossible. I don't have the smallest hands and was able to make it work. The second picture is the drivers side of the t-case, the N and 4-lo switches are located there.

Attached Images