4wd actuator not actuating

Ok. So we know the switch works.

When you say output voltages, what are you referring to?
The other wires going to the 4WD ECU that out put 12v?
Such as DL1, DL2, TL1, TL2, L4?

As of now, I kind of want to know if we have a good Ground to the 4WD ECU.
I'd want to take a test light and go from pin 12 (Black/Yellow) to pin 25 (White/Black)
That ground comes from the 3G connector you "wiggled" earlier. Maybe it's not a good ground.

You could use a meter, but I like to use a test light.
As a light let's us know it is GOOD, and not just has continuity.

If you don't have a test light.
Just use the meter and see if the ground is good. (Red lead of meter on pin 12, (Black/Yellow). Black on pin 25 (White/Black)

I'm still trying to figure out why you had the 4WD light come on by itself. But now.....it won't come on at all.
We have an odd issue, and it's going to take a lot of testing. But, I'll give you credit.
You are doing good. You are sticking in there.

 

If I remember correctly I tried pins 12 and 25 the other day and got nothing. This afternoon I was grounding it to something in the dash and had voltage. I’ll try that pin 25 ground again tomorrow to confirm. If a bad ground is the case can I run a wire from that pin and ground it somewhere else as a quick fix? Sorry I’m not much of an electrician.

I had thought it could be the ecu because of that light situation, maybe a glitch of some kind. I have another on the way just in case.

 

I'll answer that question. But let's not get too far ahead of ourself.
I know that at least part of the ground circuit is good from the 4WD switch test you did early.
As the switch shares part of the path with the ECM Ground. See the below snippet for reference.
And the fact that you regained power by wiggling the connect is kind of a clue.

Now to the question of , Can you run a new wire?
Yes, but the odds are, the issue is in the junction box. (If the ground is bad at the ECM)
And a lot of the other circuits share the same junction box.
Point being, you're likely just going to be temporarily fixing the issue.

I'd really want to have a look at the JB.

Again, yes. You can run a new ground.
But again, again, let's not get ahead of ourselves.

If the ground is not good.
By all means, make one and test it.
Then, you make the call from there.

 

I may not be interpreting this correctly but does the 2-4 switch share the same ground? Because the ground at that switch seems to be good, which makes me think the disconnect could be right around the ecu. Also do non-4wd things use that junction box/ground? If so wouldn’t they be affected as well?

 

They partial use the same ground.
They both use a different ground to the JB.
But use the same out of the JB.

Green line is shared portion of the ground.
Notice that it ties the grounds together in the JB at the 3G connector.

 

If the pin #25 at the 4WD ECU shows no ground.
Then I say the issues is on the BLUE line path in the above photo.
Which is, the connection at the 4WD ECU connector, the connection at the 3G connector, or the actual wire itself.

 

Sweet, that is kind of what I’m thinking. I’ll try to skip that blue portion and ground to something else when I get a chance later. Thank you so much for the help. I’ll report back with my findings

 

Tried piggybacking a wire from the pin 25 ground to the frame. I get 12v between pin 12 and the new ground wire but nothing happens when sharing a pin with 25

 

With out the new piggyback ground, you never got power between pin 12 and 25. Correct?
But now, with the new ground, you do get power?

 

Correct, only getting power at pin 12 when grounded elsewhere

 

Is your truck an Automatic or Manual?
We know we have at least one bad ground.
And it's in the JB. I want to verify the others that pass through that JB.

The only thing I know to do is check at the 4WD ECU.
And at that, I can only make an educated assumption based on my experience with the 2nd Gen 4WD system.
Which shares a lot of commons with the 1st Gens.

So, let's do this (If you want to continue)
On the 4WD ECU connector.
Let's test pins 9 and 22

9 = Yellow/Red wire
22 = Pink wire.

With the Plug, plugged into the 4WD ECU.
Pin 9 (Yellow/Red) should show aprox. 12v
Pin 22 (Pink) should be at 0v

With it unplugged.
9 should show NO path to Ground.
22 show Ground.

After that this check, I'm really going to have to do some thinking.
I really, really, hesitant to call it an ECU. Especially since we know we had (have) a ground issue.

 

The truck is an automatic. I can’t seem to find that JB behind the AC controls but I’ll keep poking around and test these other pins after work. Thank you so much for your help so far, this is so much more thorough than the half ass diagnosis I paid for at a shop.

 

So get this: I am getting 13.5v between 12 and 25 (maybe I didn’t have the meter pushed in far enough before). Alternatively I am getting 0v at pin 9 and 13.5v at pin 22. Why would it be backwards?

edit. I was messing with the transfer case motor timing so maybe it thinks it’s in 4x4, but regardless if the ecu is receiving/sending power something should happen I’d think

 

Give about an hour. Just got home
Let me look over the diagram. I can remember the PIN numbers off my head.

Get back to you shortly.

 

Those result are entirely possible.
As the OE diagrams do not specify what state the the 4WD is in on the diagrams.
I just assumed it would be 2WD. Which, as we know, never assume. (And I did)

The biggest issue is, I don't have a 1st gen to go test and see EXACTLY what state each pin should be in while in 2WD/4WD.
Our buddy @Dm93 literally went out and test his 4WD in every mode. (2WD/4High/4Lo) Except his was a 2nd gen truck.
The only thing I did was check the Automatic portion on my truck (his is a manual)

Anyways, Let me over look the diagrams (TL1, TL1, DL1, DL2.....) and see if I can figure out where we need to move next.

Also, @Dm93 might know what would happen if you put the actuator back in untimed.

If you want to see if anything is happening. Try putting it in 4WD and see if the reading on 9 or 22 change.
Until then, let me look at the limit switches and see where to go next.

 

Ok.

We need to see what is missing here.

With the 4WD connector plugged into the the ECU.
See what you get on the following pins. In both 2WD AND 4WD. (even if it's not working)
I know it is kind of a lot of work. But it's a must. (Even us 2nd gen guys have to do this)

FWIW, the reason we need to know what the readings are in BOTH 2WD and 4WD is because we need to see what one isn't changing states.
Then start there.


Pin 4 (Red) -----------------2-4 Switch
Pin 6 (Red/Blue) ----------- 2WD Input
Pin 9 (Yellow/Red) --------- TL1
Pin 10 (Blue/Red) ---------- DL1
Pin 18 (Gray) ---------------L4
Pin 19 (Green/Black) -------ADD
Pin 22 (Pink) ----------------TL2
Pin 23 (Light Green) --------DL2
Pin 25 (White/Black) --------Ground

Also, just so you know that I'm not blindly having you test stuff.
It's actually what you have to do. Like said, even us guys with new trucks have to do the same checks.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

The biggest issue is, No one with a 1st Gen has ever done the test on a working truck.
If they would, it would help us a lot. Then we would know FOR SURE what to expect on each pin, in 2WD, 4WD and 4Lo.

Until some one does, it's going to be a bit time consuming.

 

from what I’ve read, even if the actuator is out of timing it should display a blinking light on the dash and try to do something, which is what is confusing me

 

The 2nd Gen trucks do.
Not sure on the 1st Gens.

 

Yea I’ve read about people having the infinite blinking light on 1st gen’s and timing being the cause, but they do get the blinking light.
Thank you for the detailed explanations above as well, I’ll get under the truck this weekend and play around some more.

 

I don't know anyone with a 1st Gen truck.
Or I'd ask them to borrow theirs for a min. and check the numbers.

But, there were technically 3 different variants of the 4WD system on the 1st gens.

Manual locking hubs (1996)
Auto Locking Front Differential w/ Manual transfer case.
And Auto-Lock Front Differential w/ 2-4 Select Button.