I recently took a trip with my 2001 4Runner Limited. We got on some mild ORV trails so I decided to kick the 4WD on. When I hit the button the lights started flashing but I didn't hear anything happening under the truck. Tried the rocking back and forth method and still nothing. So after about a month of researching and troubleshooting the issue I finally was able to get it fixed. I understand that there are a lot of posts here but I'm hoping that someone might benefit from my experience.
First off, it is important to note that the 2001-2002 4Runner 4WD system is slightly different from the earlier years so please make sure you do your research. In my research, I found that the T-Case actuator on the 01-02 4Runner is identical to the actuator that was used in the Sequoia from 01-04. With that being said, I stumbled across this video that was absolutely essential in diagnosing and fixing my issue. Please watch this if you are having issues with your 4WD, it will give you a very good understanding of where everything is located and how EXACTLY it operates. Link here:
YouTube
After watching this video SEVERAL times I was able to pinpoint that my A.D.D. actuator was intermittently not working and that my T-Case actuator motor was failing and the actuator was out of time with the T-Case. Initially I crapped my pants learning that the T-Case actuator is over $1000 from Toyota and that the T-Case needs to be removed and opened in order to replace it. But, going back to the video mentioned above, you can see that the only portions of the T-Case actuator that can fail, or are prone to wear, are the motor, worm gear and rotary contacts, which all reside inside the REMOVABLE black plastic housing of the actuator. So, I ended up finding a used T-Case actuator that was removed from a 03 Sequoia that was in an accident. It came from down south so it was rust free and much cleaner than the actuator on my rig. The part came in, I swapped the housing with motor and rotary contacts onto the old actuator after manually rotating the gear inside the actuator to the correct position... (move the gear so the three "fork" contacts attached to it create continuity between ground and the mode loop the replacement actuator was in). After that I also swapped the 2 T-Case position switches from the replacement unit into my old actuator. Side note here... I tested my switches and they checked out fine but I figured since the replacement actuator came with the switches and they were in better shape than mine it was worth it to go ahead and swap them too. Also, this actuator cost me $250 which, considering those switches will cost you at least $100 from Toyota, and the fact that the new actuator is over $1000, I was happy to shell out the cash.
The second part of this is the A.D.D. actuator. I was able to find one on EBAY for about $170. It was a legit, brand new, in the box, TOYOTA OEM part. Dealer wants about $300 for these so look around before you buy. They can be found for cheaper. Anyway, replacing this was actually the hardest part. This actuator is stuffed on the backside of the front diff with the P/S rack and cross member just inches behind it. TIGHT SPACES on this, get your extensions and swivel joint sockets out! I've read that it's nearly impossible to wrangle this actuator out of that spot so I decided to remove the right front half shaft and the A.D.D. tube on the right side of the diff. I'll admit, it was a pain getting the tube off (you'll need and E14 torx socket to do it) but once it was out the actuator has a nice opening on that side to slide out from. Put everything back together (make sure to use FIPG on the mating surfaces of the actuator and the diff housing).
Replacing these items fixed my rig. This is probably worst case scenario. Replacing both actuators at the dealer would have cost me THOUSANDS. For about $400 and several hours of my time/labor I was able to fix mine. IT CAN BE DONE! There's a lot of info here, and I hope that this will be useful to someone who might also be having this issue.
