4wd System Operation & Help Thread

2009 Tacoma 4.0 4WD A/T Double Cab

 

Here you go, if you need anything else let me know.

 

Thank you!

 

what wise man people of this forum can tell me about my voltage readings? I have 4lo and 4x4 blinking, replaced both actuators to no avail, attached are my voltage reading from computer.

 

So it would seem you have an issue with the TL2 and DL1 circuits if your readings are correct.

Have you checked Connector EC1 above the front diff? It's been known to get corrosion in it and/or have broken/corroded wires there.

As for TL2 you can unplug the Transfer Case Actuator and jump Pin 6 (Blue/White) to Pin 4 (White/Black) with a paper clip then check your voltage on TL2 at the 4wd ECU again, it should be 0v if the wiring is good.

Same check applies for the ADD Actuator, jump Pin 6 (Light Green) to Pin 4 (White/Black) and check the voltage on DL1 at the 4wd ECU.

 

I will do what you suggested. The bleeding of voltage makes me thing that the wires coming from pin 24 and 13 are welded together. This must be somewhere inside the harness between ECU and where wires split between transfer case and front diff since those wires go their separate ways, see attached picture, My kid was watching multimeter for voltage changes while I was pulling on wires above transmission and voltage jumped from 4.4 to 5.7-6 volts on pin 24, well I just checked voltage again, truck is sitting like it was yesterday and now on pin 13 I have 11.8 volts where it should be 0 and on pin 24 I have 0 volts where it should be 10-14 volts wth

 

Certainly plausible.
Like I said easiest way to test the wiring is unplugging the actuators and grounding the terminals then checking the voltage at the ECU.

With the actuators unplugged the voltages should all be at 12v, when you ground the pin for each one of the limit switches at the actuator the voltage on that terminal of the ECU should be 0v.

Also the ground wires (Pin 4 White/Black) at the actuators should always be 0v.

Wiring diagram for 2010 attached below.

 

Hey I'm having trouble understanding the voltage readings on my 05 Taco that I'm getting and what to look at first as well. Any help would be greatly appreciated!

 

See if the front driveshaft is locked in in 4H, if it is then either the 4wd Position Switch is bad or the circuit is open. You can check the circuit by jumping the terminals together and checking that the voltage on the 4WD terminal at the ECU goes to 0v.

 

Hey thanks for the help! The front driveshaft was not locked or in 4h when i took the readings. Well i went to show my friend the issue today and the damn thing worked and kicked into 4H. I took some readings just because it finally got into gear and they were all correct. It took a few times trying to get it back into 2H but it finally went back. I was able to get it into and out of 4h around 5 or 6 times without issue after that. Well I figured when i was back home I out to try and check 4L and that worked as well, it clicked over and immediately started flashing again. Now I'm stuck in 4LO and i took some readings from that as well. Its just flashing however and not trying to switch. Only had a few hours to tinker today but im going to try and get back at it. Here are the readings i have now.

 

It looks like the ground for TL3 on the transfer case is your issue.
It was never good from the beginning.

You fixed the DL2 issue on the ADD by exercising the gear. This likely wiped away some corrosion on the traces.

Now you need to fix the ground issue at the Transfer Case.

Worst case, we can get you back into 2WD.
You have to pull the Transfer Case actuator and press the rod all the way in.

 

Any idea what i should be looking for the ground issue?

I read a thread earlier about getting it unstuck so I might have to do that at some point but I have another vehicle and few hours to problem solve most days.

 

Pretty much, you crawl under the truck.
Unplug the transfer case connector.
Test the Blue/White wire. If it reads battery voltage, the wiring to the actuator is good.
We can make a good assumption that the ground for the actuator is good. As the other limit switches use the same ground wire. Black/White wire. But you can still check it. I like to use a test light.

Therefore, the bad ground connection would be INSIDE the actuator.

To confirm this, flip the truck into 4LO.
Then test continuity across the pins on the actuator for the white/blue wire, and the black/white wire.
You should have continuity.

 

@AR15xAR10 looks like you have some testing to do

 

Really appreciate the help! I disconected the transfer case and I am getting 12v on the blue/white. I'm also getting continuity across the blue/white and black/white on the plug. And no continuity on the pins for the actuator. So it does seem like what you suggested!

 

Well, you are going to be mad at me.

I told you WRONG.

You should have been testing the Blue/Black wire. That is TL3.
Do the same test above for that wire.


@Dm93 we might need to get a clearer picture of the 4WD wiring.
It's blurry for me on the first page.
Or add a .pdf download.

Again sorry man..
The test I had you do was for the TL2. Sorry.

 

Hey no worries I appreciate the help! I have a much better understanding of what i'm lookin' for thanks to you. A bit late here so I'll probably have to tackle it tomorrow or monday

 

No hurry. We been here for almost 4 years now.
I don't plan on leaving for a while.....

 

Thanks again! Well i've got just under 12v on blue/black at the ecu. I also have continuity on the blue/black black/white on the plughas well I have continuity on the Pins on the actual actuator.
Going to look around again for the instructions on getting the rod moved forward again so i can try and tackle that today hopefully.