4WD problems, Round two

I think I had a post on this a year ago, but I can't find it.

I've had a lot more time with this truck to gather information and I think I've narrowed this down to a sensor or electrical problem - possibly a bad ground?

Long story short,
2H to 4H and back works fine in any conditions.
4H to 4L and back doesn't work at all unless I shut the truck down and wait about a minute, in any conditions.
Doesn't matter if the truck is hot or cold, on pavement or on dirt.


Testing I've done just today to confirm this
-Dirt driveway, Cold start in 2H, immediately shift to 4L- Works. Back up 20 feet and shift back to 4H, Stuck. Drive forward 20 feet, still stuck. Leave set to 2H while stuck in 4L and shut down for 60 seconds... Start the truck, it's back in 2H before it reaches idle.

-Drive to the store in 2H to warm up everything, paved lot. Switch to 4L, it goes to 4H and beeps- won't go into 4L. Shut it down and run into the store, come back out and start it up- goes right to 4L. Drive a circle on pavement (gross!) and now it's stuck in 4L. Forwards, backwards, clutch to the floor rolling or stopped, nothing. Power it down for a minute and start it back up, directly back into 4H.


I took the electrical side off of the rear of the transfer case to look at it- it isn't full of moisture or rot or anything like that, but the contacts weren't terrible.
https://imgur.com/a/FADw0p4
Side question, what kind of grease goes in here? I'd love to clean it out and polish up those contacts.
I did watch a video where the fixed magnets in the wormdrive motor became unfixed- but that would cause the motor to get hot or blow a fuse- mine didn't even get warm.


A lot of people talk about getting into the front differential shifter to check the electrical contacts for the motor, but as far as I know it doesn't have anything to do with 4L/4H shifting and should only be related to 2H/4H since the low gear change would be done in the rear box before sending the power up front. Or maybe I've got that wrong.



Looking for tips, anyway.
To me, this screams bad ground- why would it work after shutting down the system and restarting it, but then refuse to work moments later?

The fact that it works fine after turning the truck off and back on again really wants to tell me this is electrical, or at the very least the computer not getting the sensor data it needs.

Do I need to go into a rant as to why I can't just ask the computer what it sees and what its program is doing and why, or is that an option?

 

We can surely figure this out.
But you’ll need to do some testing at the 4WD ECU.
That is, should you want to do the testing.

Read the information in the link below.
And then get back to us with the voltages.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

Toyota "Body Grease," part # 08887-02007. Extremely expensive on a per-ounce basis. I've been looking for a substitute for some time, or some place to buy it in fairly-priced bulk quantities, but haven't found either yet. The OEM for this grease is probably Molykote, part # YM-102.

See more at: https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/page-23#post-28173976

 

That troubleshooting link is fantastic.

https://imgur.com/a/b7ncnDR
note: I only filled in the ones that didn't match

All of my 2H wiring (other than the one wire I can't seem to find) checks out- most of the 4H checks out, which seems odd to me because 4H works fine.


More than a few discrepancies with 4L voltages.
My good meter/probes are missing so some of the 0's I got could be a fluke- but seeing 12V where it isn't expected threw me off.


I got some new grease in the mail today so this weekend I might clean out that yellow schmoo and make that nice and tidy. Wrapping up a kitchen project so my meter might show up, if it does I'll double check my results

 

I'll look this over when I get in the house and see where we need to go.

 

This may sound like a silly question but just so it is established: are you shifting to neutral between going into and out of 4L?

 

For these electrical tests, the truck isn't running


For the live tests, I've tried just about everything you can try from the drivers seat. Only thing that gets it to go is to power the truck off and back on again

 

Ok question, when you put it in 4H does the 4wd light stop flashing and go solid?

If all your other voltages are normal other than DL1 and DL2 something really weird is going on in the ADD actuator, DL1 should close as soon as the actuator starts moving to the locked (4wd) position and DL2 should open once the actuator is in the fully locked position. The fact that ADD is closed says the actuator moved but DL1 and DL2 say it didn't.

 

Yes- switching between 2H and 4H the light goes solid, no flashing or beeping and I can feel it engage, usually pretty much immediately.
if I switch to 4L it just flashes and beeps, but if I turn the truck off and on again it switches into 4L just as quickly as it went into 4H- same for getting back out of 4L.

To me, that says the problem is electrical and not mechanical. For a while there I was convinced it was a heat problem because I'd let the truck cool off and then start it before getting out of 4L, but now I've figured out it only needs a few seconds with the power out

 

You mention 'clutch to the floor', do you always have the clutch pinned to the floor when trying to go into or out of 4 Lo?
I know, basic question but inquiring minds....

 

I'm curious about this as well, you have to have the clutch fully depressed and be under 3 mph to shift in and out of 4 low.
Does it beep the instant you try to put it in 4 low when the above conditions are met?
If so we need to check the clutch switch input to the 4wd ECU, I'm asuming you have a manual since you mentioned the clutch.
Still intrigued by the DL1 and DL2 voltages as well.

 

I've tried switching to 4L stopped, barely rolling, with the clutch to the floor (to engage the electrical switch) and with the clutch all the way out and then pushing it down.
I've tried in reverse, first, neutral... on pavement and on dirt. Fortunately I have a private half mile dirt road I can play on- but it isn't right at home so if I get stuck in 4L I'd have to drive home like that over a few miles of pavement

In every case, it starts beeping right away, and continues to beep until I turn the truck off and back on again- and then it immediately switches to 4L when the truck starts. Same for getting back out of 4L.
This has been ongoing since I got the truck a little over a year ago, I mostly just forgot because it's rare I have a need for 4L, while I use 4H every time I'm off the pavement just to keep it lubricated. It was a lot of fun during a heavy snow storm last winter, I bombed around town for hours and I think that's the most use 4H has seen for the life of the truck.
Heading up to the North Maine Woods again next month, and I think this time I might leave it in 4H the whole time just to exercise it. Last year I only used 4H when in the mud, and there was one point where I really wished 4L was working. Somewhere I have a photo but I can't find it... the water was up to the front bumper on the way into that site, and then it rained for three days before we called it and left. Wound up needing to winch out near the end after my rear right went over the edge

If the rain stops I can re-check dl1 and 2...

 

Ok just to be clear to get into and out of 4 low you have to have the clutch fully depressed (M/T) or have the transmission in Neutral (A/T) and be under 3 mph before moving the switch.
If it beeps imediately when you move the switch either it's not seeing the clutch/neutral signal or it's sensing vehicle speed is too high.

 

Running an errand shortly, I'll try it again when I get home. If I do this right after starting the truck, it will go into 4L without issue- but after driving for a bit it needs to be reset to work (in my previous tests)

clutch fully depressed (like I do when starting, to engage the electrical switch)
not moving (it's hard to stay rolling on dirt in the rain that slow)
switch from 4H to 4L

 

Try it and see, if it still doesn't work we need to check the clutch input to the 4wd ECU.

 

Well!

I just got in and out of 4L five times in a row in my driveway- thinking about taking it up to the hill and going up and down the road a bit...

Totally forgot to test this after running my errands so this was a cold test.

Procedure I've found that worked:
-shift to 4H however, move a few feet
-Come to a complete stop
-Clutch completely to the floor
-Shift knob in neutral (I don't even know if this truck has sensors for that, but this seems to help?)
-Hold brake
-shift to or from 4h to 4L

If I skip any of those steps, it just flashes and beeps- and doesn't retry...but for how infrequently I need 4L if this continues to work I'm happy.
I think the not retrying thing is what is getting me- when it's flashing and beeping I *assumed* it was continuing to try to make that shift and not just being annoying, so many of the different steps I've tried in the past that didn't work might not have worked because I didn't flip it out and back into 4L between tries.

Making dinner now, but after that I might go out and play, get it nice and warm then see if this sequence still works.

 

There is no neutral sensor on the 2nd gen manual and no brake input either, only vehicle speed and clutch inputs.

Yea once it beeps the warning you have to return the switch to the previous position and try again, it's not like other vehicles that will continue a shift attempt once conditions are met.

 

I do not recall seeing that little tidbid anywhere!
With the alarm going off and the lights flashing it feels natural that it would be actively trying to solve the problem


In hindsight, that would 100% explain why turning the truck off and back on again seemed to work, too

 

Yea but it doesn't, once the alarm sounds it's basically locked out until you move the switch back and try again.
You are far from the first to have issues figuring out the proper steps to get in and out of 4 low.

I have it in my thread but I guess I need to clarify it better.

 

So it's not the "can't get into 4L alarm",
it's the "try turning it off and back on again" alarm


Poor design IMO, but if it continues to work I'll take it.... I only wanted this to work once last year and so far this year I only plan to need it once... 4H works great for most of my needs. After so many years with the 2wd '99 it is absolutely incredible the traction I can get with this truck.

Still hoping to get out after dinner and try it hot, pizza is in the oven.