4WD Won’t Engage/Disengage

**RESOLVED** Read update at bottom.

Okay, here is the back story with some questions at the bottom:

2017 Off Road, 70k miles, original owner.

Out in the snow yesterday, stuck, unstuck, 4wd H/L everything working with no issues. Departing the trip I put it in neutral and set from 4L to 4H and put it in drive apparently before it completed it’s engagement. Some loud unpleasant noises and beeps. I was stuck in 4H with the 4wd dash light steady when in 4H and blinking in 2wd. It would not disengage.

Got it home, spent the day thumbing through forum posts an YouTube videos. I wanted to remove the front differential actuator, but I didn’t have fluid to top it off. I also wanted to have the part to replace it on hand knowing that it needs to be resealed to go back on, so I ordered that off Amazon and will tackle this later this week. I’m doing the work outside so I didn’t want to disassemble something that would have to be left out in the elements for 3 days.

Taking a look at the Transfer case actuator, I removed the 3 12mm bolts, found that it can’t just be removed as the gears inside are against the actuator shaft that goes into the transfer case. I then removed the 6 screws that hold the access plate on, and when we went to separate it there was a tension release and all the gears inside dislodged. Removed everything. Gears are all in perfect working order, no damage. Tested the motor, working fine. Based on other posts on this forum, apparently those gears engage the shaft in for 2wd, out one notch for 4H, 2 for 4L. I was not able to move the shaft in or out by hand. I took a mallet and with a few soft taps it worked it’s way back into the 2wd position. We re-assembled the gears (what a chore) and put the assembly back on the transfer case. Started the truck and now I just get the “2WD / 4WD Mode Change Failure”. I’m assuming this is because the transfer case is not engaged (2WD) and the front differential is engaged. I can now drive with 2wd, I was hoping that I could use the selector switch and put in 4H and it would sync up and engage. Based on some other forum posts it seems that this error over-rides the selector so it can’t be used (meaning it isn’t not engaging 4wd specifically because it’s broken, but that it’s disabled in this error state).

I’m assuming that after I disassemble the front differential I can physically slide the sleeve out of the way so the front end is not engaged? Should that shaft on the transfer case be easier to move positions by hand?

I’m hoping that ahead of disassembling the front diff, someone that has maybe gone down this road before or is more familiar with troubleshooting these comments can weigh in and give me additional insight and/or suggestions.

Obviously I’m really hoping that the transfer case didn’t take any kind of catastrophic failures. Best case scenario is I remove the front actuator, manually position it back to disengaged, button it back up and I’m back in business.

Thoughts, Ideas, Questions, Concerns?

** The resolution **
The Transfer case didn’t align properly when I went from 4L to 4H, I was in neutral and put it in drive before it completely engaged. Yes, user error.

Removed Transfer case actuator and smacked the shift rod into 2H (back fully seated into the transfer case).

My next error was caused by me not setting the timing correctly on the gears for the transfer case actuator. The was what appeared to be some alignment points on the gears and casing that we aligned it to, but those proved to be incorrect. Once reassembled correctly I started the truck in 2H, confirmed it was all engaged front ADD and transfer case, test drive was good. Tried 4H and shifted from 2H to 4H with no issues.

** Follow Up **
Went to engage 4L from neutral for the first time (did not test immediately after original fix) and I could hear it physically engage, but the 4LO light just blinks and the computer wasn’t registering it engaged. I shifted to Drive anyway to test, it was physically engaged and driving in 4L but the computer did not recognize it and now receiving the “2WD to 4WD Mode Change Failure”. Once this error is present the system will not attempt any more mode changes, effectively stuck in 4L.

I removed the actuator again, hammered the shift rod back into 2H, and re-timed the gears. Reassembled and now I have full function of all modes, shifting and operating as expected.

My best guess on why 4L was not working the first time is that I may have had one of the gears off by a tooth in the timing - enough to physically engage it, but not enough for the cams to trip the sensor flag telling the computer which position it was in.

The issue with timing the gears is that they are upside down during reinstall, and one of the timed gears is in the cover plate so from an upside down position you have to set them and align the cover plate, then sandwich them together. There is a moment before they seal together that you cannot see if they gears have shifted at all, and you have to shimmy the cover plate a bit to get the pins and gears to mesh correctly.

I have provided an imgur link of several photos showing the gear positioning and timing sequence as best as I could document. If anyone has similar issues and uses this for reference, post questions or DM me and I will answer as best I can.

Imgur Link: https://imgur.com/a/RJWLnvG

 

No input. But sub’d for the outcome.

 

I wonder if you could manually power the ADD actuator and get it to disengage. Essentially some alligator clips from a spare battery to the terminals inside the plug on the actuator.

Definitely would not try this until someone could post wiring diagrams and confirm this is even a valid idea (vs the actuator using some sort of PWM signal or something like the rear locker on 3rd gens).

But yeah, it would be easiest I would think. Hopefully then at that point that limit switches will reset the 4x4 ECU next time the truck is started.

 

Sorry OP
I did not read your post carefully enough yet to be able to give any actual input to the problem.

That said, manually driving the ADD is pretty easy. (I DO NOT know if that is going to help you yet.) I wrote about it at the end of the OP here.
https://www.tacomaworld.com/threads/4wd-actuator-troubleshooting-transfer-case-and-add.578262/

HiGHLY recommend getting techstream as the first diagnosis step, with ohmmeter as the backup

 

Thank you, this is a huge help. I just ordered the Tactrix USB adapter and I see the download link to TS in a comment on the thread that you linked me. Unfortunately, the ETA on that from Amazon isn’t until Dec 3.

So, in the mean time, w/ out cracking into the transfer case, it sounds like I can pull the connector and apply power to pin 2 to drive the motor (and subsequently, the sleeve) from 4wd to 2wd.

In a perfect world, this would clear my error and at least allow the system to attempt to function on it’s own again, and if no physical damage has been done I should regain full function.

My question is, based on your comments in your linked thread.... if I drive the ADD, should I center it, or attempt to drive to the 2wd position? I’m done for the day so I’m going to get at this first thing in the morning.

I greatly appreciate your post and responses!!

 

Yup, perfect suggestion and looks like that info on the wiring came in thanks to BigWhiteTRD. I’ll attempt in the morning.

 

In a variety of tests I have done (many of them unintentional), as long as the actuators are in valid positions, it works fine. The ECU on startup reads the current actuator positions, and drives them to the correct position.

So as long as the transfer and ADD are in positions that match (any of the positions) of the table in the linked thread, it doesnt matter if one is in 4lo, the other in 2wd... it will first run them to match the dash dial.

Where issues may arise, is that if the actuators are run too far in either direction, they wont read as valid positions on the table, and the ECU failsafes. What is most common, is corrosion on the wipers (in the add) makes the actuator read as an invalid or wrong position, to the table.

So I normally suggest running to a mid position... however...

If you are somewhat handy with an ohmmeter, I would start by reading the feedback wiper resistance for ADD and transfer actuator as the first step. See if it reads as a valid combination against those tables. If it does, then issue is in wiring, or actuator motors probably. If it doesnt read as a valid combo, try driving the actuator some to see if you can get a valid combo.

 

Any luck OP @minium ?

 

Also curious this just happened to me yesterday.

 

Hey, thank you for following up.

No measurable progress. My brother in law that was helping me reassemble the gears in the transfer case actuator found 2 videos of a hilux on YouTube, and we clearly did not time gears properly when we reassembled. Unfortunately both videos are not in English, one is Tagalog and the other is Urdu. There is a clear notch and an arrow on the red gear that we aligned to a notch on the housing which seemed logical at the time. From both videos, they are clearly indicating that it needs to be aligned off a nipple in housing instead. I had also loaned out my voltmeter, which I procured last night.

Plan today is to re-assemble that gear in the correct orientation, then work on driving that motor on the front diff to disengage the front.

I was slowed down yesterday by own only other vehicle, ‘16 eGolf, throwing several faults and not starting. Turns out that was just a bad way of the car telling us the 12v battery was dead.

Video in question:
https://youtu.be/FU8UhkcSBlI

What kind of grease would I use in that gear set? I wanted to add another dab on each of the components as I insert them so it helps keep them in position. The problem w/ this gear assembly is trying to assemble it over head while keeping them from just falling back to the ground. It’s only me now so I won’t have extra fingers there to help hold the components.

 

Yikes. How similar is your issue to mine? When I sifted through the forums I was able to find a lot of people having OTHER issues with the various actuators, but none with quite the same symptoms or cause.... or maybe they didn’t want to admit the cause of user error, which is what happened with me when I put it in drive before it completed is engagement.

Something else I’m concerned about is the shifting rod coming off the transfer case, while I was able to set it back to 2wd, it does not move as easily as some forum posts suggest - I had to tap it in with a rubber mallet, and I can not pull it back out by hand.

 

I remember a thread where a canadians got stuck in 4 but once it warmed up it went back to 2wd. Something about using 80/90w gear oil instead of the 70w toyota stuff.

 

Hah, def wasn’t that cold here in Oregon. They could have also had moisture get into the actuator housing and maybe that froze? Most issues I see on the actuators is water gets into the housing and causes corrosion, I could easily see that freezing. There is one video on YT of water just pouring out when they crack the access panel on the actuator housing.

I have 75w/90 synth in my front/rear diff and T-Case, swapped it out at 40k miles. The little that dribbled out of the transfer case this weekend when we removed the actuator was pristine.

 

What t case oil did you replace with? I just ordered ravenol per discussions on TW.

 

I put 75/90 Synthetic Valvoline , that’s what NAPA had 7 quarts of so I could do both diffs and T Case in one shot (which took exactly 7quarts).

 

I'm trying to catch up. The 4L to 4H shift that made noise is going to be the low range collar in the tcase grinding against the tcase input.

Have you confirmed that the ADD is actually engaged?

 

Calls for straight SAE 75w. Transfer case is the only fluid I would try to stay OEM with. Even though dealers don't even use it. Pony up and find the OEM fluid imo.

 

So right now the ADD is engaged, and the transfer case has been manually set back to 2H. My concern is 1. Did I do permanent damage to that collar or input shaft? I know there is no way of looking without taking apart the T case, but are those pretty solid comments? Concern 2 is why was it so hard to put that shift rod back in 2H, I wonder if after it gets moving again those components will seat themselves again?

I hope this makes sense. Once I get the actuators gears timed and put back in place, and disengage the ADD, is it going to get screwed up putting it back into 4H.

 

I can't offer any help in the trouble shooting or repair.

I do know the assembly should not need a mallet to force it into place. Something isn't quite aligned.

Suggest to put the mallet back in the tool box.

You might try a dab of basic bearing grease GC-LB to help hold parts in position as you assemble.

 

You could always mash it all back together and then go to the dealer and play stupid. Who knows maybe it won’t be that expensive.