4wd System Operation & Help Thread

Update on my 4lo blinker. It finally came back. After running a few tests and getting nowhere with it, I traced back the ground to the junction box and stuck a piece of wire in behind connection 19 at connector PA, at the junction box, then ran it down to the ground lug just above the floor where a few ground wires are all terminated to a terminal block that’s bolted to the side of the wall.

With key on and making connection, 4lo keeps blinking, but when I turn the key off then on again, gone!

Thanks a million guys for guiding me through this. Just in time for the snow.

Here’s a few pics of the crude fix I have made, until I get some wire from work tomorrow and make a proper splice/termination.

 

Hey guys, I’ve picked through this form and come to a point I’m ready to ask some questions.

-2006 Tacoma 4wd
-Stuck in 4wd with green light 4wd and 4Lo flashing. This was progressive, as in the past, I could eventually get it to pop back to 2H. 4lo has been finicky for years.

I took the easy route and replaced the Actuator without any luck (guessed but didn’t test). Cleaned all connections and checked EE ground, no changes. Finally grabbed the multimeter and following the awesome write up @Dm93 started here.

Following the shift knob in 4hi chart I found that TL2 is showing 12v. It should be 0. All other wires are as they should read assuming 4H.

I can not shift out of 4H to test other options

Any advise on where to go from here. I’d assume that wire is broken at some point… what should I test now? Where should I look to find that wire on the other side.

Thanks everyone. This has been super helpful so far.

 

So we need to check wire integrity on the TL2 circuit.

Unplug the Transfer Case Actuator and use a small paperclip or jumper wire to jump Pin 6 (Blue/White) to Pin 4 (White/Black) then check that TL2 goes to 0v at the 4wd ECU.

 

Dang, that was an incredibly quick response. Thank you.

Jumped 6 to 4, retested TL2 and went to zero. Also tested TL2 at the transfer case and it showed 12v.

 

So that would suggest that the issue is in the Transfer Case Actuator, you said you replaced it but are you sure you got the timing correct?

 

Ok. I did not clarify. I replaced the ADD Actuator, not the transfer case actuator.

How will I know if I have the timing right when I replace it with a new one?

Can I take it out and run any diagnostics myself? Such as loose connections, bad hoses etc?

also, if TL2 is 12 volts in 4h, does that not mean it is open/broken somewhere? The table you made us shows it should be 0v in 4H. Just trying to understand.

 

Oh ok, when you said actuator I assumed the transfer case actuator.

You will need to carefully remove the cover and make sure the large gear remains in place and note the position it's in so it can be reinstalled in the exact same position if it is removed.
I'd bet the TL2 contact has a corroded spot, you may be able to just remove the cover, clean it up, and put it back together.

Well we tested the circuit by jumping TL2 (Pin 6) to Ground (Pin 4), it went to 0v at the ECU so wiring integrity is good therefore the issue must be with the contacts in the actuator.

 

Ok. I’ll take a look inside and get back to you. Thanks!

 

Got it off, looked to be a small bit of water inside and some grime due to a cracked hose. Fixed the hose and sanded down any corrosion. Put it back together and still having the same problem.

here is a before and after it was sanded. Still a little bit of corrosion but didn’t want to take off to much material.
I wonder if that corrosion is beyond repair?
Any advise before I order a new part?
Thank a ton!

 

Yea that is pretty common for the vent hose to do that, that's why we try to tell everyone to check it regularly.


It may be beyond fixing but did you clean the contacts on the gear as well?

 

Yeah, that’ll be good to know for the future. I did clean the contacts. Pulled the entire unit apart including motor, cleaned and regreased. I’m wondering now if it’s the motor that’s shot? I don’t hear anything when I turn my 4wd knob. Typically you’d hear a couple clicks.

 

That contact trace is probably pooched but you could try pulling the cover again and turning it to 2wd (fully counterclockwise) then put it back together and give it a go.

 

So, I finally got the transfer case actuator and have replaced it with a new one. No changes. Still blinking 4lo/4wd and am stuck in 4H.

Checked tl2 and it is still showing 12v in 4H. Jumper Pin 6 (Blue/White) to Pin 4 (White/Black) then checked that TL2 goes to 0v at the 4wd ECU and it did.
I still do not hear a motor engaging. When switching btw modes. Nothing happens.

Is there a reset I should do?

Thank you as always.

 

Did you verify timing?
I'd set the Transfer Case to 2wd (gear fully counterclockwise) then try it and see what happens.

 

It worked!!! Not sure why. Took it apart again. Cleaned everything out forced into 2WD. You are the man!!!! Thank you. I’ll let you know if all stays in one piece and runs strong. 4lo works as well. That has been out for years. Thanks again!

 

Nice, it may have just been because it was in that specific spot with TL2 open so the 4wd ECU just locked out immediately on powerup.

 

You're a brilliant man. Thanks for the trouble shooting and you’re patience. More than anything… thanks for always getting back you me!

 

Wow! What a great thread. Thank you so much @Dm93 for starting it and all the info and help as well as all the others that have contributed.

I just got back from a trip from CO to CA, to WA back to CO. Had to use the 4 Hi over Snoqualmie as usual this time of year. Timed it just perfect for the most traffic and heaviest snowfall of the day too. But, all went well.

When I got home to CO I did my oil change and lubed the propeller shaft and checked things over underneath. I also took it out to check 4Lo since I haven't used it in a couple of months. Low and behold when I went from 4Hi to 4Lo I got the dreaded blinking 4WD light on the dash along with the beeping when I went from neutral to drive.

Using the information in this tread, I'll be doing a lot of checking and testing tomorrow. Gonna need a heater in the garage.

One thing I did find was a brittle, cracked vent hose on the transfer case. How hard is it to run a new hose as far has maneuvering and fitting your hand up?

Thank you all! And Go Bears!

 

If your truck is an Automatic, it is a pain in the ass.
The vent hose is routed on TOP of the transmission.
I'd buy a vacuum hose splice from the parts store and just replace the portion at the transfer case.
The line doesn't usually crack up top.

 

@TnShooter, thank you! I had that feeling as I was laying on the freezing cold garage floor.