MarzVegas

@99SC4Runner
Copy on the ADD actuator. I am ordering a new one from Toyota as well as the ADD switch. I have verified that both my vacuum solenoids were functioning properly but since the filters were missing I felt that they should be replaced. I found a set in a wrecking yard today so I grabbed them along with the vacuum lines and chamber for good measure. They only charged me $3. When I got home I verified that they are good so once the actuator and switch come in I expect to have that part handled.

My big question right now is on the transfer case actuator. I can jump mine to 2wd(ground pin3 and power to pin2) and then to 4wd(ground pin2 and power to pin3) but then it seems to lock up. I assumed that this meant that the motor was worn. I checked inside and found that it looks to be in excellent condition. Confused. I figured I would just replace it anyway so I went and checked out a used one today and it did the same thing. I don’t understand why and feel like it must be missing something? Do you have any idea why that is happening?

In regards to the transfer case, I saw that you can remove the triangle-shaped cover plate on the actuator and remove the gear inside which allows for removing the actuator without splitting the case. I have done that successfully. Is there a reason you don’t recommend that?

I haven’t checked the L4 position switch, the neutral position switch or the center diff lock indicator switch yet but I am heading out to do that now. I’m going to start by checking the L4 and Neutral position switches continuity while they’re in the case. I don’t think I can do that with the center diff lock switch as I don’t think the diff is locking. Any suggestion on the best way to remove those three switches? It seems like short of dropping the case you’d have to get to them from the top by removing the shifter mechanism?

In respect to the center diff lock actuation. I thought that pulling the shifter back to H4 locked would cause it to engage but I wasn’t clear if it was a switch or a mechanical action. I figured that since the center diff is locked via a switch on the dash if there is no rear diff lock that maybe it was a switch. Is none of that correct?

I think my ECU is not the issue at this point but that may prove to be incorrect. I also think the 4wd 1&2 switches are good from my testing but that may also prove to be incorrect.

Thanks very much for your help

MarzVegas

@99SC4Runner I checked my L4 and Neutral position sensors last night and they expressed continuity as expected when the shifter was in L4 and Neutral respectively so I think I’m good there.

Won’t have the ADD parts until early next week so I’m going to get the vacuum solenoids installed and plumbed this evening. It would seem that the solenoids are activated when the button on the shifter is pressed. Is that correct?

If so they should be able to be checked that they switch correctly while installed but not connected to the vacuum system. Is that correct?

That part aside I am still trying to get the transfer case actuator figured out. As I mentioned my seems to work a couple of times when jumped then freeze up. I don’t know why? I took it apart and re-indexed the wheel. When I reassembled it I got it to go from 2wd to 4wd and then it froze up again. I can buy a used one for $200 locally but it seems to be doing the same thing. I don’t really have the money so I don’t want to buy it for no reason. Please let me know what you think.

Thanks very much for your help

99SC4Runner

The brown and blue solenoids VSV on the left inner fender are what controls the front diff vacuum actuator for going into 4wd and back out to 2wd.

I would start with replacing the VSV switches and seeing if it starts working normal.

If the actuator on the other t-case behaves exactly like yours does when you jumper the terminals on the plugin, then chances are your actuator is good.

MarzVegas

My research through the internet, the Toyota shop manual by trial and error has led me to this hypothesis. On a ‘99-‘00 4Runner Limited, when the transfer case actuator shaft sets in three different positions. I believe that when it is “all the way out”, or what I will call “First Position”, it is in 2wd. When it is in the middle, or “Second Position”, it is in 4wd with center diff locked. When it is all the way in, or “Third Position”, it is in AWD with center diff unlocked. The position of the actuator shaft determines the continuity state of the #1 & #2 4wd switches. When in 2wd both switches are open and neither should express continuity. When in 4wd switch #1is open and switch #2 should express continuity. When I. AWD with center diff unlocked both switches are closed and should express continuity. The transfer case actuator motor should rotate to move the actuator shaft from all the way out(2WD) to all the way in(AWD) when the “4WD” button is pressed. The actuator motor should rotate to move the actuator shaft to the middle position(4WD) when then transfer case shifter is moved to H4Locked. The front diff, the center diff, the transfer case are independent subsystems that must each be properly functional for the system to work as a whole and not give the flashing lights of doom. In my case the vacuum lines for the front diff had been misrouted to and partially disconnect from the vacuum solenoids. Testing showed that my vacuum solenoids were working fine but as they were missing the filters (that can’t be replace) I went wrecking yard scavenging and was able to pull the entire vacuum system for $6. I installed it this evening and was able to successfully achieve front diff engagement. Unfortunately my happy dance was to be short-lived. The known issue of an unstable A.D.D. actuator and switch came into play all too quickly. After connecting the front diff vacuum system suddenly had no more flashing lights. Prior to connecting the front diff vacuum I had reindexed and reinstalled the 4wd actuator with it set in 2wd. When I pressed the “4WD” button I got four steady green lights with no orange center diff light. The actuator only held for about 20 seconds and then the flashing lights showed up like at a high school party and crushed the groove. The front diff actuator is apparently stable when in the unlocked state so as long as the transfer case is in 2wd there are no flashing lights. The minute I press the “4WD” button. The lights start flashing. However, at that point the culprit is the 4wd actuator not the from diff actuator. I am not sure what is wrong with my 4wd actuator. I took it apart and indexed it to the best of my ability based on what I’ve been able to sniff out on YouTube and from there I was able to jump it into 2wd. I then installed it to the transfer case with actuator shaft set all the way out(2wd). When I pressed the “4WD” button it engaged what seemed to be AWD as there was no center pumpkin lit up just four green tires. But then the lights started flashing. I think I’m going to let it rest for a bit until the new A.D.D. actuator and switch arrive. If all goes well, once I’ve installed those parts I hope to be able to eliminate that from the possible criminal list. My transmission shifter is so worn the the bushings are gone so I picked up a used one. I’m going to get it all refurbished then when I remove the old one I will also rebuild and reseal the transfer case shifter housing. The transfer case shifter boot appeared to be all torn up so I picked up a clean one at the wrecking yard. This evening when I began to plan the replacement of the transmission shifter assembly (gotta plan ahead to avoid screw ups) I found the boot wasn’t worn but had been cut. A mess of duct tape had been used to seal it back up. With little success. Anyway, Ima get all that squared away while I wait for the front diff parts. I’ll be pulling the transfer case actuator to reindex it at least one more time so I’ll check the diff lock indicator switch at that time. That’s the only other part that I haven’t verified yet. So I still have some sleuthing to do but I’ve narrowed the possible suspects quite a bit. I’m hoping that when everything else has been set correct the 4wd actuator will resync and start working properly. If not I’ll be at a loss as to what the matter is. Anyone that made it here pkwaae give a shout. Peace

USCG4runner

I know this is OLD but When you replaced the front sensor did the light stop blinking as soon as your turned on the truck or did you have to shift in and back out of 4wd? I have identical issues with my 2000 limited. Tore apart the actuator and manually put it back into 2wd and just replaced the front sensor but still have the blinking lights. I’m nervous to attempt to shift it in and out cuz finding the time to get back under my rig is less and less these days. Appreciate the help!

MarzVegas

I would be more than happy to help. I have put a silly amount of time into learning the detailed ins an out of the craziness that is the 1999-2000 Limited 4wd system. I’d be happy to pass on all of what I’ve learned. If you’re interested send me a message. Thanks

toverturf

Thank you for this thread. I had the same issue and replaced the front diff sensor and it shifts in and out of 4WD easily. Tested my old one and nothing would happen when I would push it in.

toverturf

As soon as I started it up after replacing it I could hear the transfer case disengage and the blinking light went off.

Rickster0418

Read every post on this thread. Thanks to the OG who created it . Your reply was very similar to my problem . Hopefully your still around or someone can chime in.

I have a 2002 sport. Unfortunately I have the two 6 pin electric actuators for the tcase and front add.

my problem is when switching to 4h I get the flashing tires and differential light. 4 low same thing. Truck spins all 4 tires when I put it on the jack stands so it’s engaging. When I activate the center differential locker I get solid tires and solid orange light so basically anything un locked i get the flash

so far I’ve replaced all 4 switches 2 on act and 2 on the tcase . Replaced the 4wd ecu. Tested the front a.d.d buy supplying power to pins 2 & 6 motor worked both ways . No continuity on pins 3 & 4 in either position.

I’m kind of lost the moment .

Hcrp333

[QUOTE=DoubleZero4x4;50707886]I replaced the front diff switch today (PN 84222-35070) and low and behold the 4WD works like it is supposed to - It even comes out of 4WD too.

Hey man thank for this post I’m having the same issues but can I ask how can I differentiate the front and back sensors that need to be replaced? And I saw you offered to send pictures to a fellow user. Could you email me picture as well? I tried to private message you but not allowed. My email is (Haley at site wide logistics dot com - *all together* )shooting my shot at your email posted in 2008 in hopes it’s still active.

Rickster0418

finally fixed it. Removed the transfer case switch and engaged the 4wd with a buddy while watching the metal rod with an inspection mirror Angled. Plunger was not traveling all the way into the transfer case leaving the switch barely engaged. Solution . Filed another metal sealing washer about half the thickeness and used two washers the lift switch off the plunger un ohming the switch. Works perfect. Mostly likely my transfer case motor is getting weak
or it’s misaligned . For now it’s good to go

bkingsle8

I have a feeling my issue will be similar - 2001 4runner SR5 - lights flash when I try to go into 4x4 - we have changed both TC actuator sensors with new OEM Toyota parts, cleaned TC actuator and motor armature and tesed, replaced 4x4 ECU module with a warrantied/refurbished one from Module Experts in FL, installed a new AISIN front ADD actuator - lights still blinking continuously. I can, however, get it into 4x4 by jumping that front TC sensor plug with a wire. I was thinking of filing down my washer, thinking the rod isn't pushing the sensor ball in far enough.

What a pain to diagnose.

Is Charchee still with is - or a good Toyota tech in New Mexico who has an idea here?