4wd System Operation & Help Thread

Yea after looking at your voltage tests again I do see that your selector switch voltages are not correct in 4H, I guess I saw the ADD at 0v in 2H (maybe your probe didn't make connection?) and my brain stopped there. Srry it's been a busy last few days and my brain hasn't been all there lol.

 

I’ll post new results with new switch this weekend. Should be here in a couple more days. Thanks for your help!

 

I put a test light across the pins at the 4wd ECU as I don’t have someone currently to flip it for me. At the ECU, tm1 and tm2 got no light when flipping the switch. Would that lead to potentially the wiring being faulty/damaged?

 

New selection switch works. Truck shifts as it should. 4hi on the fly. 4 low stop with clutch.

the old one had a broken tab and was not making contact internally.

 

Was the 4wd system not already locked out when you tried this (no flashing light)?

Nice, glad that's all it was.

 

I just want to say a big thank you to the ones who put this thread together. Very well done and informative.

I originally had flashing 4hi and 4lo about 2 or 3 years ago. At that time I pulled apart the front diff actuator, it was filthy inside. I cleaned it up, put it back together, refilled the diff with fresh fluid and I was fine for about a year. Then I started getting the flashing lights intermittently. If I needed 4wd I would shut the truck off and restart until I had no lights, and then shift. The past few months I basically had constant flashing lights. So today I dug into it.

First thing I did was the pinout test at the control module. Right away I had wacky readings for tl1 and tl2. The rest mostly checked out. So that pointed me to the transfer case actuator. And what do you know, after pulling off the 3 bolts and the cover (really easy), I found much of the same gunk that I had in the front diff actuator. It was nasty. Cleaned it all up and put it back together and it worked. But I made one mistake. I pulled the gear out to clean the little fork contact without marking the location first. When I reinstalled it and took it for a drive, it was evident I was just slightly off on the timing of the gear, I had a noise or two after shifting back to 2hi. So I pulled the cover off and rotated it by hand. I figured out that 2hi was counter clockwise until the peg on the gear hits the peg on the case. But it didn't feel like it "snapped" all the way in like it did in the 4hi position (tested by spinning the front driveshaft), it would go to 2hi and the front driveshaft would spin free but I didn't feel that positive engagement, it felt like it was only shifted halfway. I also remembered about how much I was off by on the gear visually. So I moved it about 2 clicks on the splines, now I could feel a positive engagement in 2hi when I spun the gear until the pegs bottomed out full counter clockwise. Closed it back up, did a couple tests in the dirt shifting through all positions. Much better, just like it was before I had any flashing lights.

So I guess the takeaway from this is to mark the position of the gear before you remove it. And if you don't, it is possible to time it by hand using the feeling of engagement in 2hi/4hi and spinning the front driveshaft to confirm the position.

 

Glad to hear this thread helped you out.
Yea keeping the gear in time is crucial for the actuator to work properly, it can be re-timed but sometimes it take several tries to get it right.

 

Big props to you for taking the time to put this together with all the diagrams and pinout voltages. I couldn't have done it without you. Well, maybe I could have but it would have taken much much much longer to pinpoint the issue. Yeah, the timing was pretty simple once I realized where I went wrong, spin the gear until you feel the engagement (it's really obvious), then spin the driveshaft to see what position it's in. If you get 2hi and 4hi correct then by default 4lo will be correct. I was only off by about two splines so hopefully no damage done.

 

I don't think there's really any chance for damage, it's either gona work or it isn't.
The main thing is the contacts on the gear need to match the position of the Transfer Case.

 

Anybody out there know the size of the 3 bolts that hold the Transfer Case Actuator together. I knw they are 2 inches long but don't know the width. 6MM or 7MM? Just snapped the head off one trying to undo it so need to get more before I continue. Thanks

 

Just took one out and measured since I was next to my truck.
6mm x 50mm x 1.0 pitch

 

Wow, that was fast. Thank you very much. Also, thank you for this incredible thread.

 

I just happened to be out here working on a tractor and my truck was right there so I grabbed a creeper and popped a bolt out right quick.

 

Need help ASAP.

My 08 Tacoma 4x4 V6 does not engage at all. Once knob turns to 4H it just blinks. No beeping. Same with 4L.

I back probed the lower harnes connector on the 4x4 ECU. The picture are my readings. Not sure if I can narrow it down to one issue I believe it may be multiple issues. Some help and advice would
Be greatly appreciated! Mahalo.

 

Everyone, and I mean everyone.... check that your vent hoses that attach to your actuators, are not split on the ends. IF they are, cut a little off and reinstall.
I think this is the majority of the problems we have with these units. I think...
In my opinion, this can't be repeated enough.
And @Dm93 is the man!

 

Srry for the delay, been kinda busy.
Assuming your testing is correct and I'm interpreting your results properly (I'm asuming you 13v not 0.13v on TL2 and TL3?) it looks like your 4wd selector switch isn't working properly.

 

I probed the incorrect for 2-4 and LO. Apparently it’s green lol. Little color blind. But I tested those two on the top right of the espoused colored wires. Blue and green.

 

I'm confused, 2-4 should be grey and LO should be blue.

What about my question on the voltage on TL2 and TL3?

 

There are two harnesses that connect to the ecu. For the probe test. Are we probing both or just one? Because one harness there is a grey and the other doesn’t. However the one that doesn’t have a grey has every other color wire the chart calls for testing.

 

All the limit switches (TL1 TL2 TL3 4WD L4 DL1 DL2 & ADD) are on Connector F13 (B), the 4wd Selector Switch inputs (2-4 & LO) are on Connector F12 (A). They are all going to be smaller wires, the larger wires are Power, Ground, & Motor circuits.