Transfer Case Actuator/4wd troubleshooting including how to manually shift the transfer case

First off, if you are reading this and you are stuck by the side of the road because you can't shift the transfer case do this:

1. Remove the 3 bolts circled in #6 below
2. Rotate the brown plastic gear by hand (2nd photo in #8 below). There are 3 positions (2wd, 4wd and 4Lo). I believe 2H is fully counterclockwise with 4H in the middle position and 4Lo in the Full clockwise position.
3. Put the housing back on and go about your merry way
4. Note: this does not mention the ADD, if you are trying to get into 4wd, you also need to make sure the ADD is in the correct position. If you are trying to get out of 4wd (like I was), you can ignore the ADD and still safely get your truck home. I wrote this because I couldn't find this info when I was stuck in the mountains and couldn't find it, so hopefully it helps someone.

Hi all, I thought I'd share my 4wd troubleshooting experience for future reference in case people have the same issue and it's not the ADD.

What Happened (symptoms):I was going up to Big Bear and started sliding around a corner so I thought I'd put the truck in 4wd but the lights were just blinking. I got it in by turning the truck on and off a few times and was able to get it back in to 2WD the same way for the ride home luckily.

Troubleshooting setps:

1. I tried the OBDII scan tool and got no faults. I believe you need techstream to see the 4WD ECU codes, but I'm not positive.
2. Since most of the literature on the boards focus on the ADD, I figured, oh this is an obvious problem and is likely my problem. I took that off and soldered the contacts including the contacts on the limit switch and verified the motor worked by jumping the motor power to battery power (make sure to do this without the actuator assembled since the limit switch won't cut power in this configuration.
3. I checked the resistances per the 3rd gen writeup which is great but only applies to the ADD on the 2nd gen and apparently is different for the transfer case actuator (https://www.tacomaworld.com/threads/4wd-actuator-troubleshooting-transfer-case-and-add.578262/) (note that the connector image above is for the harness not the actuator so the numbers are flipped on the actuator side)
4. Since I didn't check resistances before I took the ADD off (you can/should check before you remove it unless you want to do the solder mod preemptively), I just put it back in and tried the system out...still wasn't working as expected and was the same as before (t-case actuator made sound, but ADD never disengaged, lights kept blinking)
5. I also noticed that when I flipped the 4wd selector switch the transfer case actuator was definitely spinning, this incorrectly led me to think that the problem wasn't there. OK, time to dig into the Transfer Case Actuator. I looked at the FSM and there are quite some diagnostics that I didn't find super useful. I would recommend the resistance measurements here as a quick sanity check though this doesn't seem to be a common failure mode: between 1 and 2 is going to be your motor resistance so if that is open, you're motor either isn't connected or it's fried. (I didn't actually check this because I could hear my motor spinning when I changed the selector switch, but it's good to check this especially if you don't hear the actuator motor)
6. The FSM has a heater relay test, but since I didn't have one, I didn't do that test. I should note that visually I saw the vent hose on the actuator housing was cracked.
7. I know I forded a river on my previous off road trip and the truck had been sitting for a few weeks since then. I did the following measurements next: I don't remember exactly which shift position I was in but I did have about 17 Ohms instead of the <1 Ohm specified
8. So, I took off the 3 hex heads off that you see circled in the pic above (10mm socket or wrench). What I found was a housing full of water and corroded contacts: (you shouldn't have any liquid or see any blue, that's the corrosion) The circular electrical contacts you see in the housing are the switch circuits listed above that tell the ECU what position the transfer case are in. They make contact with the wipers on the gear that's still on the transfer case:
9. What I should've done here is just wipe the grease and corrosion off the wipers that are on the gear and leave it in place because the wipers were not actually corroded, but I removed the gear from the housing and now I'm not 100% it went back clocked the right way.
10. Anyway, I dumped the water out of the housing and wiped the grease and corrosion out of the housing and found that there was pitting on the outer trace (not a great photo because there is flux on the trace):
11. Then I tinned the trace by applying flux and a thing layer of solder to avoid future corrosion. You may want to wick excess solder away to avoid damaging the wipers on the gear. Also, don't forget to clean away the flux as that can be corrosive as well:
12. I put some lithium grease in it and put it all back together. I put the gear back into the actuator as best I could based on my photos and I think it is working, but I haven't tested 4Lo yet. I may need to remove the housing again and reclock the brown plastic gear.

Disclaimer: I don't have any miles on my fix yet and don't promise it to work, but it was worth it to me to avoid the cost of a new actuator or doing the FJ swap. For those considering the FJ swap, I recommend reading this to know how to manually shift the stock actuator/transfer case. Knowing this now makes me think the FJ swap is mostly for if your actuator is absolutely fried or for looks/feel.

Ok there you go folks, feel free to let me know if you have questions or disagree with anything above or have any further insights to share.

 

Great write up.
If you don’t mind, I will add it to this thread.
https://www.tacomaworld.com/threads/4wd-system-help-and-information.696298/

 

Oh man, I wish I had found that post when I was messing around with all this. That’s a great compilation and I’m almost not sure my post adds anything, but thanks!

 

Your’s is definitely worthy of posting.
Very well explained with good information.

 

thanks fro posting this with photos, glad to se you can address the pitted contacts.

 

Just to clarify, if you're stuck in 4wd and manually shift to 2wd, should you pull the ADD to make sure the diffential is disengaged if you are going to need to drive it a while before you can repair it?

 

no need to do that but you can if you want.

 

I had a flashing 4x4 and 4 lo light. I have found that the wires leaving the actuator are cracked and on is completely sheared. If I follow from the six prong connector to the first connection that is where the cracked wire is. Does anyone know what part number this wiring harness is?