My 3rd gen center diff lock appears to be stuck on/engaged, I can't seem to switch it off. I was in 4HI in the snow/gravel with 4 green lights, pressed the center diff lock button and after 4 green lights and center orange light blinking for 10 seconds or so they all went solid. Upon exiting the snow I pressed the center diff lock button and 4 green and center orange continually blinked but never went back to solid.

I can press 4wd button on transfer case and it comes out of 4WD easily after a short time of blinking 4 green and center orange. It also easily goes back into 4WD as well.

I've tried several variations of D to N to R at low speed, switching the center diff on and off, including transfer case 4H, N, and 4L, including steering slightly left and right during these variations. I do hear an audible click in the front dash area when I press the center diff button, like a solenoid is switching, but no other sound from the drive terrain, and 4 green and 1 orange either continually blink, or they go solid and VSC light comes on. I can confirm that the center diff is locked while in 4WD from the heavy steering.

I've done some searching on the forums, but wasn't exactly clear what my next step should be?

This was the culprit to my problem, this solenoid is a common problem on the 4runner after a number of years. Watch the video. Hopefully this works for you as it is an easy fix. I had to buy the solenoid from the dealership, could not find it aftermarket.

2002 4Runner 4WD Repair - YouTube

Revisiting this issue as my 4Runner is still suck with center diff lock on when I shift into 4WD. I'm trying to identify the part numbers for these transfer case switches so that I can just replace them.

The linked youtube video (https://www.youtube.com/watch?v=T1ZbLxFTrH4) replaced the two switches that are on the driver side near or on the transfer case actuator to repair the 4WD not engaging. I believe these are part numbers:

84222-12010
84222-35070

Same part but two different locations.

This yotatech thread mentions "Center diff lock sensor which is on the passenger side of the transfer case", which sounds like it could be more related to my center diff lock stuck on issue:

4WD won't disengage on 99 4Runner LTD - YotaTech Forums

But I'm not sure of the part number for this switch.

I'd basically like to replace all the switches on the transfer case that I can get to except the ones on top that requiring dropping the transfer case. I think there are 3 of them. The two near the transfer case actuator, and another one on the passenger side that is the center diff lock switch?

Haven't been able to find a diagram that clearly displays all of these switches, so would appreciate any help in identifying them.

Thanks!

Confused - if 4wd engaged with center lock and using 4wd side button it all blinks/turns off, then all is good.

How do you know it is stuck in center lock position if lights blink/turn off?

Mine has gotten very near silent after repeated use, especially the center lock.

So if I go from 2WD to 4WD by pressing 4WD button on transfer case shifter my lights go into blinky mode, I believe it's all 4 green and center orange continue blinking. I can also tell from heavy steering that the center diff is locked. If I then press the center diff lock button on the dash all 4 lights will go solid, so center diff lock mode is good. If I press the center diff lock button again to come out of it they go blinky again and stay there.

In a nutshell I can get into and out of 4WD, but cannot get out of center diff lock.

There's 2 things that happen when the center diff is locked. The front ADD engages and the transfer case motor locks the front and rear driveshafts together. With the light blinking, put the vehicle on jack stands and try to turn the front driveshaft with the transmission in neutral. If the front and rear driveshaft turn together then the transfer case is still "locked". If the front driveshaft moves separately from the rear driveshaft and turns the front axles then the front ADD is still engaged. Help us help you by performing this diagnostic procedure and reporting back what you have found.

Thanks for your help. Finally got back to this. With the lights blinking and car on jack stands the front and rear drive shafts are locked, they turn together. Front differential is also engaged, front wheels turn.

I pulled the two transfer case switches that are easy to access on the driver's side of the transfer case. I performed a continuity test on them and I believe the rear switch is working correctly - it gradually transitions from no continuity to almost full continuity as I depress it. The front switch has no continuity anywhere in it's stroke, it remains completely open. I tried cleaning it up with solvent and it remains the same. I'm hoping this is my issue, as I believe these switches are supposed to close as they are depressed.

I've searched around and looked at diagrams and I think these are the appropriate part numbers for these two switches. I think I'll just replace them both.

Front: 84222-12010 (NO. 1)
Rear: 84222-60081 (NO. 2)





Does it sound like I'm on the right track?

I'd also like to replace any other switches that are easily accessible. Are there any others I can easily get to on my '01?

Thanks.

Unfortunately replacing Transfer Indicator NO. 1 didn't seem to make any difference. I got excited because it tested bad (no resistance), so thought for sure this was the culprit. Transfer Indicator NO. 2 tests okay.



I've been studying the transfer case diagrams in the TSM and it looks like I have the VF3AM multi-mode transfer case with the electronic center diff lock actuated by the dash button (not the pre-2001 J-shifter actuated).

The indicator switches in the TC diagram near the shifter (3 - L4 and 4 - Neutral position) seem unrelated to the center diff lock positioning. I guess the J-shifter version of the TC has a center diff. lock indicator switch on the passenger side, but mine has a screw plug (5) in this location.



Any suggestions on what to check next?

Have you checked the ADD position switch yet? Should be located near the front add actuator.
When changing 4wd selections can you hear or feel the front actuator or transfer case 4wd actuator moving or attempting to move?

If all your position switches check out good, as a last resort you might consider pulling the actuator cover off the back and making sure it's not got water in it and the contacts aren't corroded. Just be VERY sure that you don't remove the wheel with the contacts that's actually attached to the motor.

Last summer I went through a hood-deep water crossing without realizing my actuator vent tube had dry rotted and fallen off the nipple, and filled my actuator up with water. I pulled the cover and cleaned it up (gently sanded the corrosion off the contacts in the cover) and smeared white grease all over everything and buttoned it back up. It's been working fine over the last year.

I have not checked the front ADD position switch. Does the '01 electric actuated ADD have one?

I made a video of the actuator sounds when 4WD and Center Diff Lock buttons are pressed.
https://www.youtube.com/watch?v=vpLPIrMVYYc

In summary:

1. Pressing 4WD button on TC shifter, I hear at least two actuators cycle, one on the TC and one forward of the TC (assuming this is the front diff ADD)
2. All four 4WD lights will blink in dash. At this point the front diff and front propeller shaft are locked, the front propeller shaft is also locked with the rear propeller shaft. I.e. center diff appears to be locked.
3. Pressing Center Diff Lock button (ON), I hear an actuator cycle on the TC and all 4WD lights go solid.
4. Pressing Center Diff Lock button again (OFF), I hear the same actuator on the TC move from previous step, after 3 seconds all four 4WD lights start blinking. Front diff and front propeller shaft are still locked, and front propeller shaft is also locked with rear propeller shaft.
5. Pressing 4WD button on TC shifter (OFF), I hear the same actuators from step 1 (at least two) cycle, one on TC and one forward of the TC. 4WD lights turn off and front propeller shaft spins freely.

So it seems pressing the Center Diff Lock button is cycling an actuator on the TC, but the center diff lock never seems to physically unlock.

I listened/watched your video. It sounds like at least the transfer case actuator is working. I would put my hand on each actuator while a friend pushes the buttons to make the actuators function and feel for their operation.

I've attached (hopefully) a parts diagram for an 01 that shows the ADD position switch labeled 84222C which I would definitely recommend removing and checking for continuity just like you did for the other 4wd switches.

Just to recap for me, when the 4wd lights are off and the tires are off the ground do the front and rear driveshafts spin separately and do the front tires both spin together?

Attached Images

 

Of course as soon as I post this mine starts acting up again...

Since my 4WD was still working I didn't prioritize fixing my center diff lock issue over the last 6 months, but now my predicament has worsened. Now I can't go from 2WD -> 4WD at all. I click the 4WD button on the TC shifter and I don't hear any sounds on the TC or ADD actuators, 4WD indicator lights just continue blinking. Previously it would at least go from H2 -> H4L (both actuators - center diff lock LOCK), but just would not continue into H4F (center diff lock FREE). I'm starting to suspect it has something to do with my TC actuator.

I have not yet checked the ADD position switch on the front diff, but I will do this next. In the mean time I tested transfer indicator switch no. 2 (the rear one on the TC actuator) and it tested bad, so I replaced it with a new one but still can't go from 2WD -> 4WD.

After watching this excellent video on the Sequoia 01-04, which has apparently a nearly identical TC actuator, I'd also like to be prepared to test my TC actuator by jumping it directly.

sequoia 4wd troubleshooting - YouTube

The TSM says you can cycle the TC actuator from H2 (2WD) -> H4L (4WD and Center diff. lock ”LOCK”) by using a heater relay:



In the Sequoia video the gentlemen instead jumps two terminals together, and then supplies +/- to two other terminals to cycle the actuator through the modes.

Can someone tell me based on the TSM diagram which terminals to jump and which ones to supply +/- to move from H2 to H4L?

In the end you were right and the actuator turned out to be the problem. Even though transfer indicator switches both tested bad over the last year, replacing them didn't fix the issue. I carefully pulled off the actuator cover and sure enough there was some water and corrosion:



As you recommended, I carefully removed the cover and made sure not to pull the gear with the contacts off, so as not to mess up the actuator timing. Then carefully sanded the outer ring which was corroded and cleaned everything up. I also pulled the electric motor cover off and there was some water and corrosion damage there as well, on the brushes and where they contact the part that spins (don't know the term). Cleaned all that up and put it back together. Bench tested the motor and it was working. Put the actuator cover back on and everything is working now.

Note that I did have a cracked breather hose on the actuator cover, but never has the truck been through water crossings or any extreme water events. Just the typical rainy weather in California, and a few trips to the snow. Still water somehow got into the actuator and mucked things up.

Some posts I came across were asking about actuator timing. On my '01 this is what it looks like in 2wd, with the gear turned all the way clockwise and the shift shaft all the way out:



And if you open up the electric motor cover this is what you will find:



Thanks for everyone's help who contributed to this thread. Looks like I am good, for now!