4wd System Operation & Help Thread

TL2 should be at 12v if it's confirmed the Transfer Case is in 2wd so something is going on there too, you said you had the Transfer Case Actuator apart?

You would need to backprobe DL1 (Pin 6 Light Green) at the ADD with it plugged in to verify it reads the same voltage as at the 4wd ECU.

I just made another chart to make it easier to log and post actual voltages, I'm also adding it to the top post.

 

Thanks dm93. Confirmed TL2 at zero volts at ecu key on. Pin 6 on ADD plugged in key on confirmed at 12v, matching ecu read.

I did have the transfer case actuator apart. I took the cover off to inspect the contacts, and it actually looks brand new. Everything looked really good and clean, and I ohm tested between pins 5 and 6 on the transfer case actuator to confirm timing to 2h.

 

If you didn't remove the gear the timing shouldn't have been affected but if you did it would need to be retimed.
To ohm check the limit switches you would need your meter ground on Pin 4 and then check the limit switch pins.

 

I did in fact remove the gear. Upon reassembly I timed according to the video linked on the thread (using a straight edge to line up); it took an attempt or two. Lined up for 2h matching both actual state of ADD and Tcase and confirmed with resistance between pins 5-6 on tcase actuator (let me know if there’s another/better test to confirm this).

I tested the 4wd and Lh4 limit switches on the tcase actuator and both checked out.

For ohm testing the limit switches in the ADD I think I have three questions:

1. This is what you refer to above with ground on Pin 4?

2. do you by chance have ADD pin to limit switch reference? I didn’t see in the thread - read through the whole thing a couple times in the last couple days

3. ADD limit switch testing to be done with plug attached and key on?

i really appreciate your expertise and patience. I’m trying to take my time and really test carefully and get it right.

 

1: Pin 4 is the limit switch ground on both actuators so for resistance testing with the actuator unplugged you want your meter ground on Pin 4.

2: If you post your year I can post up the full 4wd system wiring diagram for your truck.


3: For doing voltage testing yes, if you are ohm/continuity testing on the actuator itself you want it unplugged if that makes sense.

 

Sm93, you’re the man. It’s a 2006. I’m away for the evening now (morning children obligations) but will ohm test each, grounded on actuator pin 4 with actuator unplugged in the daylight and post the results. Excited to narrow down.

 

Here you go, yea I'm goin to bed too it's midnight here.

 

Okay; Tcase Pins ohms tested grounded to 4 (I tested twice but can again if anything seems wrong or improbable):

1 - no continuity
2 - no continuity
3 - no continuity
5 - continuity
6 - continuity

Getting ready to test ADD pins.

 

Okay; ADD actuator close to same:

1 - no continuity
2 - no continuity
3 - no continuity
5 - no continuity
6 - continuity

 

That suggests a problem in the Transfer Case Actuator unless it is not fully in a position.

3 is TL3
5 is TL1
6 is TL2

If it was plugged in that would put them at

3 is TL3 0v
5 is TL1 12v
6 is TL2 12v

That would be correct for it to be in 2wd.

 

Thanks dm93. If I focus on the ADD for a second, pin 6 shows internal continuity as it should for 2h. Shouldn’t it ground to zero though ans not show 12v or am I backwards on that? Meaning is it possible the ground from the ADD is ineffective?

So TL2 internally grounded but shouldn’t be and therefore giving 0v (actuator issue). Although notes indicate it goes to 0v at end of 2h shift so maybe grounded is okay?

DL1 internally grounded and should be but still showing 12v (possible external ground issue)

i could be backwards on that. But if right can I physically ground add pin 4 and test or is that bad?

sorry I’ve edited this post more than my own resume.

 

Yes continuity through the pins to pin 4 means they should be at 0v with the system plugged in.

It seems that way, if you look at where the voltages should be it doesn't line up with any of the valid positions.

Possibly, you would need to backprobe Pin 4 with it plugged in and the key on and verify it stays at 0v.

 

I misspoke on tl2 - it’s showing 0v which lines up with internal ground (post above edited) and also tells me external ground on tcase pin4 is intact. Given the notes on original post circuit closes after 2h shift so I think this may actually be okay??

now let’s turn to pin4 on the add. Back pin test plugged in and key on gives me just over 11v! Did we just solve my issue?? Can I physically ground pin4 to chassis and test the system?

 

Yes you could, if it works then we need to determine where the break is.

 

Winner, winner, chicken, dinner! DM93 - this is a BIG day. Four-wheel-drive hasn’t worked since we bought the truck. I can only imagine the costs and irrelevant parts purchased if we would have taken it into a shop. This post is so kick ass! Not only do the pins read right, but it goes in and out of four-wheel-drive now no problem. (tells me I got that timing right bullet dodged there). So I am in California where it’s been dumping rain on me all day (actually been raining for a week straight), I need to warm up next to this propane heater for a few, then I am open to tips on tracing that break?

 

Visual inspection at the plug for add actuator seems okay. Both actuator grounds seem to terminate at a common location - do you know where this is?

 

Yup it's the top connector of the Interior Junction Box No2 behind the glovebox.
If it's good there then you need to check connector EC1, I'll have to go look where that is I'm not sure off the top of my head (I think it's above the front axle but I'm not sure).

https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/page-19#post-28171042

 

So if I remove my manual ground and back pin test pa8 with key on I either have voltage (break is after that) or no voltage (break is between that and ADD actuator plug) - does this sound right to you?

 

Correct.

 

Okay so pa8 yields no voltage on back pin test. Further confirmed by ohm test beep (continuity) between back pin and chassis. I guess the tcase actuator grounds here also with no issues so it’s logical.

so the break is between pa8 and actuator plug, straight run of wire (no other pit stops)? That’s kind of a bummer if so.