Another 4x4 not working thread

Hello everyone,
I have an 04 DC, pretty clean truck, but it has one issue: 4LO won't come on.
I have been browsing several threads and I can't seem to find my exact issue.

4HI works flawlessly, but when I try to engage 4LO (in neutral, brake pedal down) nothing happens. No lights (on dash or button), no beeps, no whirring actuator noises underneath the truck.

Underneath the truck it looks great, no corrosion at all, the actuator connector is spotless and the vacuum line is solid.

I'm sort of at a loss, and am hoping to be pointed in the right direction. I'm wondering if something is wrong with the PCB where the button is or maybe the 4WD computer?

Thanks for reading!

 

Did you have your foot on brake pedal?

 

Yes I did. I will update the original post.

 

Make sure you stop the truck completely. I would try 4HI at low speed then stop completely, put in neutral, brake pedal down, and switch to 4LO. Try this to see if it works.

 

Ok, will do. I had a 4th gen 4runner with a v8 with the notorious stuck actuator, and that at least made some mechanical noises when I pressed 4LO and would beep at me until I stopped trying. This just does nothing, so I was suspecting that the actuator wasn't even getting a signal from the computer.

 

Just wanted to add that this did not work, unfortunately.

 

Watch this video...it covers the solution from one end to the other.

https://www.youtube.com/watch?v=TmuEVv1neVQ

 

Thank you. I came across that video in my initial search. I am not exactly having that same issue, as my 4HI works fine but 4LO just does nothing, no blinks or anything. I have inspected the actuator and the contacts all look great.

 

Here's the section of the transfer system from the FSM. It gives instructions on testing the components towards the end.

 

After you hit the button for 4 lo, try driving slowly for a little bit (like 2 miles an hour). Mine won't engage just sitting, I have to be moving.

 

I have tried this as well. When yours isn't engaging are you at least getting a blinking 4lo light?

 

I'll double check tonight, but I'm pretty sure I am.

 

That's where I'm stumped because I'm getting nothing. It's not even getting to that point. After looking at the above FSM section shared, I think I'm going to be spending some time checking the PCB where the buttons live and the 4wd computer.

 

On my 2014 same process I did according to the manual, 4lo doesn’t wanna work and sometimes when it does it doesn’t want to get out of 4lo. The trick that seems to work for me is from 4hi and in neutral, the second I switch to 4lo I release my foot from the brake and it has worked every time. Try that. If that fails for me I’ll take it to Toyota, but they want $140 just to look at it not including what has to be fixed, ridiculous!.

 

Or call upon our hero, @empty_lord

 

Good chance the actuator is to blame.

 

I'm new to the Tundra, so please forgive me...
I bought my 01 LTD 4WD because it was the only one I found in a year that didn't have a rotten frame, but it had a terrible shudder in 4Hi above 20mph. It also needed differential bearings. After replacing the diff bearings, the 4Hi issue seems to have ceased. What? That makes no sense. Any ideas?