It might be worth removing it, popping it open and seening what's up. A little contact cleaner and dielectric spray inside might bring it back to life.

-Charlie

I didn't bother even opening mine up. Literally just banged it around on a hard surface then put power to it to see if it would cycle. Once it cycled I just cycled it a handful of times then put it back in the truck.

Sorry, that comment was for the OP - if it is working for you, keep it that way!

-Charlie

Well I got one of those pricey, NLA relays and installed it the other day. I drove about 40 min. and my 4runner still went in and out of 4wd just like it should. Today we took a drive in the mountains for a walk and it would go in and out of 4wd all the way to where I turned off to the deeper snow. Sil fun of bilfitch!! No 4wd. No mechanic or exorcist in sight so we took a short walk. Come back 20min. later and hop in to head back. Yup, works fine now. But only for about half an hour. Is it possible the mechanical part in the transfer case, that presses the button on the 4wd detection switch doesn't make a solid enough pressure, when the case warms up? Just before the 4wd function stopped altogether, the relay could be heard clicking and then buzzing and I could make it change by wiggling the transfer case lever. Anyone else hate intermittent electrical gremlins, especially when you can't duplicate them at home where the tools are?

In order for the 4wd indicator light to be on the transfer case 4wd switch and front add switch both have to be depressed. If your 4wd light is on the dash when the 4wd isn’t working then I don’t think the switches are the issue.

When the 4wd isn’t working when it’s supposed to be on can you spin the front driveshaft by hand?

This was happening with my 2002 sr5 4runner it would sometimes engage the 4wd and sometimes it wouldn't. I found out it was the actuator attached to the transfer case. It was more cost effective to buy a used transfer case with a working actuator already installed than it would have been to replace just the actuator on the old transfer case.

You have a different transfer case. You have a vf3am transfer case which uses an actuator to change 2wd/4wd, but the OP has a vf2a transfer case which is a fully mechanical transfer case that uses a shift lever for 2wd/4wd change.

Thanks for the responses. The 4wd light on the dash does operate and when it is on, we are definitely in 4wd and when it is off, we are definitely in 2wd. If I read the wiring diagram correctly for this transfer case, the relay is powered and operates to switch, when the it gets a ground signal from the 4wd mechanical "detection switch" on the transfer case. Power also goes to the 4wd light on the dash, which only lights, when it gets a ground signal from the "ADD position switch" on the axle disconnect mechanism. When I get the chance, I plan to run an alternate ground wire to the relay with a switch, so that if I lose 4wd again (when I need it most, of course) I can feed the relay another source of ground to see, if that make the relay work. Sure, that's the ticket. What could go wrong?

I referenced my 2000 EWD and I agree with what you said. ADD position switch is for the 4wd indicator light. 4wd transfer case switch is used to ground the relay for the VSV.

I can't remember, did you remove the transfer case and add position switches and clean/check for continuity when depressed?

You should be able to hear the ADD relay click in the passenger footwell when you shift in and out of 4WD (2H <-> 4H) - that should be an easy test whenever you are having the problem. If the relay doesn't click, you have a detection switch problem on the TC. If it does click, then you have to check the VSVs, actuator and position switch for the front diff.

Your understanding of the electrical portion seems correct.

-Charlie

Well if anyone is waiting with baited breath, I think I have finally figured this problem out. I put a switch in the dash, that grounds the relay at the same connection, that the transfer case switch does, when 4wd is engaged. Drove for an hour or so to where I needed 4wd. The relay did not work. I flipped the switch giving the relay the correct ground and presto! 4wd. The T/C switch was no longer providing the ground as previously, but the dash switch worked, grounding the relay, triggering the VSVs correctly, engaging the ADD and that in turn showed up as a the green 4wd light on the dash. If I get really bored or ambitious, I may pull the T/C switch again. The aluminum washer under the switch is fairly thick. I may replace it with a thinner one or just grind it down to half thickness to create a more positive connection. Not feeling bored or ambitious just yet. Thanks to all for contributing their ideas. Oh, and I now have an extra T/C switch and relay.

did you ever figure out this issue 4ruiner, because I am having this exact same problem