2002 Tacoma 4wd front differential not engaging

Newbie here and need help. I have a problem with front differential on my Tacoma not engaging. My truck is a 2002 Tacoma v6, AT with standard shift lever for 4wd- (no button to shift it into 4wd). I do not get a light when I shift it into 4hi or 4lo. I jacked it up and put it on stands, engaged 4wd (shifted it to 4hi) had a friend watch differential and it turn, but front wheels do not turn. I also tried 4lo and same thing. There is a small hose on the ADD and I tried to trace it out. It looks like it goes to the 2 capped off lines by battery. I read where some people say this is only a vent line. Is this correct or is it a vacuum line? I removed the kick panel on drivers side and tried to hear relay click when I shift into 4wd, but I never heard any click(I read on a thread where you are supposed to hear this). I found a black box with tag that said- Computer, 4wd control and is a Denso brand. I unplugged it and checked to see if it had voltage to it. It did on 3 of the pins. The ADD is very difficult to get to on the truck. Looking for suggestions on what to do now. If I have to remove the ADD actuator, are there any videos or directions on how to do this. Anyone had this problem and fixed it?

 

There are a bunch of plugs that go into the tranny. One activates your reverse lights, another your ADD (I believe), some others do some other things. Mine fall out from time to time. I'd check those. I have PO disaster franken ADD, so my experience is different. But I'm pretty sure those gadgets by the fuse box activate the ADD back and forth via that vacuum line.

 

I hope this helps. This is for an 2003. I will search and see if I have anything more specific to your needs.

 

hope this helps.

 

Hey mate, I had the same issue with my truck last year. So.i took the add out to see if it was the problem, and it wasn't. It was low on front diff oil. So make sure you check that first. If not could be a PVC vavle I think its called( not %100 sure) but definitely check your diff oil.

 

Low oil prevented your front diff ADD from working??

 

That ADD was working fine, but once i filled the front diff up it worked just fine again.

 

Did you ever figure this out? I think I’m having the same problem.