About a week ago I got a great deal on an 07 V6 4WD that had a known issue with 4Lo not working. Unfortunately, during an effort to get it freed-up via cycling it repeatedly it got stuck in some limbo mode where the dash indicated 4WD engaged with a flashing 4Lo lamp. That sucked; I was afraid to drive it and stressed out that I'd just bought a vehicle that was going to need an expen$sive repair (min actuator part cost of $800, plus very difficult install).

So a read a bunch of threads. Seems like the classic issue is that the actuator gets gummed up thru lack of use. Nothing actually fails, it just gets stuck. Given the state of my truck, I figured that was likely.

I found a post by BlackWorksInc where he posted a training document that was really useful.

I also pored over the factory wiring diagrams; these two were very useful:

Actuator/Control wiring:


ADD Control/wiring:
http://houseofun.ms11.net/Misc/Toyota/ADD%20wiring.JPG

Thru some of the other threads on the subject I found that user Woodless identified the actuator motors as Mabuchi Motor RS-385PH. Consultation of the online datasheets for these motors indicated that the maximum operating voltage is 30V, significantly higher than the typical in-vehicle max of 14.7V....

I know that electric motor torque rises with applied voltage. BlackWork's .pdf indicates that the expected operational voltages for these motors is 10.5-14V. There's a lot of available torque between 14 and 30V. I wondered if I could break the actuators free by supplying the motors with >14V, which I intended to supply to the actuators directly from the connectors to the 4WD computer.

Worked like a charm! Time to eat, more in a few...

Interesting... Well I'm glad I could help.

Not sure how much I'd recommend over-voltaging the motors as you have to keep in mind that if the motors are "locked up" or have a lot of resistance that's a lot of voltage/current feeding through a single commutator until it starts spinning.

BUT, I suppose when you have nothing else to lose; it's worth a shot.

And that's exactly it. It seemed like my next course of action was going to be tear the actuator down and deal with trying to time it, etc... First, I didn't feel like I had much to lose, and second, given the relative strength of the xfer case parts *and:* the 30V upper operating limit (not short term limit, *operating* limit) I judged that short term blips of higher voltage weren't going to be immediately threatening.

AT THE SAME TIME... I wanted to only use as much voltage as needed, AND the application was very short term. In my case, 15V was enough to drive all three motors back and forth against their stops. ANOTHER CAVEAT: Once I heard the actuator reach its stop, I cut the power.

I have an adjustable voltage power supply that allows me to dial the voltage up or down; this was helpful for a couple reasons (more below) but probably isn't necessary.

OK, to summarize where we are now: I used this method to successfully return function to my transfer case actuator without having to take it apart, or really even go under the truck.

Collection of disclaimers: This worked for me. I was careful, I'm not inexperienced in this sort of thing, and I was absolutely aware that it could go completely south if I wasn't paying close attention. If you try it, it's at your risk exclusively. I'll not be held responsible if you jack your rig up. Shouldn't, but it could happen.

See the above images. I started by locating the 4WD computer, which on my '07 V6, is mounted to the panel below the glove box, then determined which plug was the relevant one by carefully examining the wire colors.

Note well that it is best to not turn your truck on with the 4WD computer disconnected; says so right on the module.

My starting symptoms were such that I believed the ADD was in the wrong spot. The dash light indicated 4WD, but I wasn't convinced that 4WD was actually engaged. The first step was applying power to terminals 3 (red) and 6 (black with white stripe), then reversing polarity and applying power again. These wires power the actuator, so success is hearing the actuator in the front diff moving on at least one of these cycles, then continuing to cycle as you reverse polarity and reapply power.

The next step is to verify that it's in the right spot. In my case, I was shooting for 2HI because that's the most useful mode and if I was going to freeze my truck I wanted it there. As a result, I needed to make sure that the ADD limit switches indicated that the ADD actuator were in the position that corresponding to that state. Looking at BlackWorks PDF, (page 2, bottom right), the appropriate switch states are Closed on DL1 and Open on DL2. The way to check this is to verify continuity to chassis ground on DL1 (terminal 13 at the connector, light green) and no continuity to chassis ground on DL2 (terminal 12 at the connector, pink w/ blue stripe). I found that it was possible to get the limit switches into theoretically impossible states, so it may take some care to get it where you need it. The limits of travel are likely NOT the desired state; you're looking for somewhere in the middle, and I found that when trying to get the actuator correctly positioned reducing the drive voltage was helpful because it slows down the actuator motion. Once I had the ADD where I felt it ought to be (confirmed by the limit switch state from the training document) I hooked up the computer, made sure my 4wd switch was set to 2HI, and turned the truck on without starting it. This was successful and the 4WD lamp was no longer lit. 4Lo was still flashing....

I then turned my attention to the transfer case actuators. Overall the approach is the same: Use 15V (or more?) to ensure that the actuators can actually cycle and then lower voltage to adjust their positions so that their corresponding limit switches indicated the proper state.

I started with the the TM leads (conductors 2 (green) and 5 (blue)), as these control the Low/High actuator which was my original issue. Honestly, it cycled right away and never seemed to stick at all when driven with 15V. I absolutely had to screw with it to get the switch states correct (again, I was looking for the 2Hi state, so I wanted TL1 closed, TL2 open, and TL3 closed) but eventually got it there by driving the actuator with ~7V to keep it nice and slow).

Unfortunately, getting the desired states on T1/2/3 was not enough to shut off my flashing 4Lo lamp. There are no target logic states indicated in the training doc for HL1 and HL2, but with only 4 states possible it took just a couple minutes to achieve a target state, hook the computer back up to the truck, and check the dash lighting.

Overall, this took about 3 hours to do. In that time I was able to take my truck from being in a limbo 4WD state with a known issue with 4Lo to *fully functional*. As I said earlier, the next stage would have been risky disassembly of the actuator itself; I determined that the potential risk here was sufficiently low to try it.

I fixed my sticky actuators with electricity and logic, and now I'm the proud owner of a fully functional '07 with 72k on it. Paid less than market as well, so I'm pretty pleased.

What a gold mine of a post! I have the exact same problem as you. When you said this:

How exactly did you change the logic states for HL1/HL2? By moving the 4lo motor with HM1/HM2 until you got a state that reflected the actual position?

SUPERLATIVE effort by op.
a million likes

Excellent information and Great Work.

Yes, exactly. Look at BlackWorksInc's PDF. On p3 in the upper left corner you can see that HM1/HM2 drive the high/low shift motor and infer from that that HL1 and HL2 will change. Again, there are only 4 states possible (on/on, on/off, off/on, off/off) and by trying them one-by-one I found the state that made the controller happy.

I'll point out again that once the actuators are broken free they'll move more slowly/are a LOT easier to control if you lower the applied voltage. It was hard to deliver precise 'pokes' of voltage to HM1/2 at 15V; IIRC 6V was about perfect but YMMV.

Luck!

Edited to add: Having re-read your question, I wanted to add a bit more. You asked, "...until you got a state that reflected the actual position?" In my case, I believe the 4wd actuators jammed up mid-shift, and the computer went into 'limp' mode because the actual position (which is always reflected by the switch logic) didn't match the mode it expected. I had to step thru each potential logic state, reconnecting the computer and turning on my Runner each time, to find the state where 'actual'='expected' and the 4wd computer stopped freaking out.

Bet yer ass I run thru EVERY MODE EVERY DAY I drive it now

Thanks to all who have contributed. This is fantastic info. However, I have a V8 all time 4WD and there are fewer pin-outs and switches. I rarely use 4L, less than 4 or 5 times in 8 years, but recently required it. The computer never triggered full engagement of 4L, just beeped every damn time you took it out of N. However, it's in 4L. I assume the pin / actuator got stuck mid-way and now it won't budge. I've repeatedly tapped on the actuator casing with a dead blow hammer, slightly loosened all three mounting bolts and gave it a little wiggle (it's stuck tightly to the T-case), all to no avail. Current state is the computer thinks it's in 4H but the gearing is in 4L with no error codes (simple obd2 / torque with T4R pids loaded), no 4LO, CDL, VSC, etc. lights illuminated.

I found this thread, along with several others, and originally decided I'd see if the dealership could get her back into 4H. I dropped it off after being assured a seasoned technician with deep knowledge of T4R 4wd issues would work on it. At the end of the day, I was informed I needed a new actuator, $2800 but they got it out of 4L. I asked the tech how he did it and much to my surprise and worry, he said it wasn't in 4L when he got it. "Got it out on the road and hit 55 with no problems". I should have asked him what the RPMs were at 55 because it was still in 4L when I got it back. So, I'm back here doing his job.

Using http://www.toyota-4runner.org/1440184-post11.html and the diagrams here I recorded the following information.

Using pin #s instead of circuits since the documentation is for a V6. (Voltage readings are with the engine off) 4WD ECU.

F9 Pins = voltage:
9 = 10.8
11 = 0
15 = 11
16 = 11
20 = 11
22 = 0
24 = 10.5

F10 Pins = voltage:
17 = 10.8
26 = 0
24 = 10.8
23 = 0
22 = 8.9 (curious if this is normal given the range for the V6 is 10.5-14)

Voltage to the actuator harness confirmed for pins 1 and 4 (HM1/HM2). If the pin is not listed, there wasn't a wire in that location excluding the top rows.

When put into 4L, 4LO flashes and you can here the actuator buzzing with the pulse of the 4LO light. I'm trying to decide if I should pop the cover or order a variable DC power supply and push 15 volts to the motor.

Does anyone happen to have the V8 version of the 4WD Operation Quick Training Guide? Any thoughts you might add?

Thanks again!

Edit: After cracking her open, I'm not convinced it's the actuator unless the motor is dead, which spins freely. Both polls on the motor are reading 11.55 volts. Next step is to unplug the 4WD ECU and apply voltage to HM1 / HM2 and see if she moves.

Inside the case: https://imgur.com/5MvqyLx

Edit: Ok, I had some confusion on which motor controlled 4H/L and CDL. CDL motor functions fine, unfortunately the 4H/L motor is underneath the CDL motor mounting, which will not come loose. I assume you have to separate the actuator assembly from the t-case in order to remove that mount? The assembly will separate slightly from the bottom but it won't budge from the top. And after reading more DIY posts, I don't want to do this since it sounds like the 4H/L shaft is spring loaded. I do not hear anything when applying 12v to F10 pins 1 and 4. Seems like the motor is dead or has a bad solder joint. Am I at a dead end here?

Hi everyone,

I read this thread hopeing to find the specific 'wire gauge' that is indicated for repairs on the "transfer case actuator switch". I need to splice the damaged end.

Does anyone know?

Thanks.

Just purchased a 2008 4Runner that wouldn't engage 4Lo. I used the OP's method and was able to get the H-L motor working again. FWIW, it took 25 volts before the motor would unstick. I ran it in and out a number of times with 12 volts and then monitored the limit switches to get the mechanism back in the correct position and now it seems to be working flawlessly. Many thanks to the OP.

I just bought a 2008 T4R as well. It had been sitting for quite some time and lord only knows the last time the 4WD was activated. It was not able to go in to 4hi.
I tried the OP procedure and was able to get the 2-4 actuator to function. It did take 20 volts though to get it unstuck.

A couple observations.

One, I am building a new garage so I was working in the driveway, which has a slight incline to it, during the process of moving the actuator I found a neutral position and the truck started rolling backwards. Scared the crap out of me but I was able to reach over and apply the parking brake. So be careful.

Second, once I was able to get the actuator working I had a hard time getting it back to the 2hi position but I could get 4hi quite easily. So I put it in 4hi, moved the selector to 4hi and plugged everything back in, I was hoping the truck could sort it out. Sure enough it did and was in 4 hi and when I selected 2hi it had no issues.

I have not tried 4lo or locking the front diff. I am assuming they are stuck as well but at the moment I really only need 2hi and 4hi so I will tackle those two next year.

Thanks so much to the OP for posting this up, it really did help!

Matt

Hey everyone, I'm very excited that I found this thread as I hope this fix will also cure what ails my truck. Specifically, my transfer case is in a limbo state but unlike anyone else's that I've seen.

The truck will go from 2wd to 4hi without issue, the problem started when I shifted into 4lo. It worked, but when I tried to go back to 4hi and eventually 2wd. The truck will disconnect the front drive so when I go back to 2wd it is in-fact 2wd(confirmed by getting it on a lift and observing the wheels). But the vehicle still drives like its in 4lo.

So with all that said, my reason for posting is to ask the hive mind about order of operations. Should I leave it in 2wd and try to zap the 4Lo motor? or should I put in ito 4wd(Hi or Lo?) and then attempt to put power to the motor? Does it even matter?

I hope this makes sense and thank you in advance for any advice!

any idea where I can find the wiring diagram? the houseofun.ms11.net link is broken. Thanks in advance!