4wd System Operation & Help Thread

I completely understand, since you say a frame swap was done there could be damage in a harness somewhere. All it takes is a nick in the insulation of a wire in the salt belt and it will corrode until it breaks connection.

 

22
21
20
19
18
I’m in the fifth one from the top.

 

Ok just making sure, I couldn't tell for sure from the picture.
If you do happen to run into anything that doesn't work then ground the other end of that wire as well but as far as I can tell the cut end just goes to the engine block and doesn't ground anything else in that section.

 

Thank you for all your time and help.

 

YOU GUYS!!!!!!! you have no idea how amazing this thread became! I’ve been chasing this exact problem with these exact symptoms for over a year with too much money dumped and parts throw with no positive results yet.

just checked my grounds at the block EE as well and that end reads out 0vdc and at the interior buss pins 18+19 have about 1.8 vdc or so. Hope that is high enough voltage on a bad wire/ground to turn the system whacky.

what do you guys think? Pin 18 comes from the block ground EE and then leaves on 19? But where does it go to further in case that’s not my failing wire


I’m beyond excited to snip this wire tomorrow and hopefully it all works finally

 

If you have 1.8v between ground and Pin 18 of connector PA and it's good at the block then the wire between the block and connector PA has to be open or corroded.
Does the system work with a scanner plugged in?

 

Cruise control comes back with scanner plugged. Dunno about 4wd. Have had it unplugged for awhile but I found the print of the ground buss from earlier pages which is great. Have had the code for canister as well

 

I'd bet fixing that ground will fix all your problems related to that ground then.

 

I’m betting y’all are right this has been the best thread. Man I’ve been throwing parts at this stupid thing for awhile. Although now at least I get the whole system and am better with a meter.

 

That's why I've been trying to promote testing instead of guessing and trying to figure out how everything is supposed to work to develop testing methods to determine the problem when it doesn't work.

 

Agreed now. I hadn’t come across anyone with any of the same common problems until now and then just lost interest.

 

I had someone else before @N919HJ that we had gotten far enough into testing that I was pretty confident they had a bad ground but they never came back.

 

Ooohhhh I will let you boys know

 

Side note: Don't (ever) make the mistake of turning the knob from "4-HI to "2-HI" and turning the key to "off" before the system is finished doing it's thing and completing the change. (like I did recently to run into Dunkin' Donuts). It won't be happy and might (will?) make you pay! I had a blinking dash light when I fired it up again. Switching the knob back and forth: no change. Re-starting: No. I didn't dare try selecting "4-Lo". It finally returned to normal when I put it in Drive and moved it forward a bit: It sent me a message by giving a loud "clunk" that went right through the frame up to my seat and then turned off the light. I can't imagine the drama if I had done this in "4-LO". Let's just say it left an "impression" on me to say the least. Two days later I held my breath tested it/switched it >>in my driveway<< and it was like nothing ever happend previously. Lession learned! I will never do this again.

Kinda like flying: when you screw up and adjust the wrong control or select the wrong switch and it scares the heck out of you: your brain breaks that connection permanently and forever and you never do it again. Ever. You might do something else by mistake, but it won't be the same mistake... especially if you don't survive.

 

Sounds like the driveline was in a bind, sometimes when that happens you need to drive in reverse a few feet to relive the stress on the driveline while shifting to 2wd. I have had 0 issues with mine but it gets used quite a bit (at least the transfer case actuator anyway because I have the 2wd Lo module), it does clunk sometimes when going to 2wd just due to driveline bind-up. The system seems to be relatively robust providing no water get's into the actuators and they get operated at least once in awhile. It's just harder to diagnose than some other vehicles when it does break simply because of it's inability to set codes or show live data.

 

That seems the likely cause. I follow the periodic 'exercise steps" about once per month, both underway and stopped. The worth of doing this is very apparent
when stopped: On my truck the first actuation to both 4-HI and especially 4-LO and back always seems a little "coarse". I do it 2-3 times each and the following changes go nice and smooth. Really brings home how important it is to do this.

 

Mine has always been pretty smooth going into 4h, going in and out of low and out of 4wd sometimes gives a little clunk but that's pretty normal for any 4wd system with gear engagement. The clutch type systems that GM and Ford use don't tend to do that.

 

Thank you! Your Tacoma 4WD tutorial is one of the best docs I have ever read. I read it "cover-to-cover" when I joined the forum. The last trucks I owned before the Tacoma: 1987 Bronco had manual locking hubs, and 1989 S10 Blazer Sport with 1st generation "shift-on-the-fly" 4WD. The manual hubs and and stick operated xfer case on the Bronco just worked. The S10, while it was a beautiful truck that I loved, had a "gizmo" vacuum/electric transfer case actuator that needed to be replaced every year. It had a New Process Gear supplied x-fer case (Chrysler). The xfer case was indestructible, but the $200 actuator switch was sub-par. GM replaced that part three times: two out of warranty. I know it's "old guy thinking", but if my Tacoma had manual locking hubs and a stick-operated xfer case, with all the other history and reputation: in my mind it would be the perfect truck.

 

Thanks for the kind words, if you haven't seen it already I just recently put together another thread on some other systems of the truck and diagnostic tips you may want to check out.
I'm currently working on adding diagnostics for the P0500 code but progress has been kinda slow.
https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/

 

Will do! Thanks! You're BATMAN!