Hey folks! I have a 96 4Runner Limited with stock e-locker and push button 2-4 transfer case shifter. Automatic transmission.

I was wheeling yesterday in 4lo and 4hi with no problems, suddenly my 4x4 light goes out and I'm not getting any power to the front wheels. Light never blinks or flashes.

I can shift my transfer case with no grinding. I cannot rotate my front diff driveshaft by hand even in 2wd.

After a lot of research (especially comments by TheDurk) I tested vacuum on the twin VSV nipples. I get vacuum on the red/brown VSV in both 4lo and hi. I get no vacuum on the blue VSV, regardless if I'm in 4lo, 4hi, or 2wd.

I followed the two vacuum hoses from the VSVs to the front diff to make sure they're both connected. I sprayed carb cleaner around all the vacuum hoses to check for leaks. No leaks.

I unplugged the electrical connectors on the twin VSVs and used a 12v test light - no current on either connector, regardless of being in 4lo or 4hi.

I inspected the one way check valve coming off of the manifold which appears to be working fine.

I used a test light to check the current on the 20a fuse for 4wd inside the cab, current is good but I replaced with a new fuse anyway.

I unplugged the two side-by-side 27mm switches on the transfer case (drivers side) and checked current on each one (while in both 4lo and 4hi) - I get no current - however I'm not sure if I'm supposed to.

I removed the 27mm switch on the front diff (which I believe is only to turn on the 4x4 light in the instrument cluster) and thoroughly cleaned and checked for broken wires.

With every electronic connector I unplugged and tested, I cleaned thoroughly with electrical contact cleaner and added dielectric grease inside each connector.

Considering that I get no current at either of the VSV connectors - I'm leaning toward this issue being a bad 4WD ECU. I believe a 96 with auto transmission has no 4wd relay, right? I checked the wiring under the passenger side kick panel and did not see any relay.

Any other ideas?

 

There should be 5 total position sensors, 1 on the front diff, 2 low on the transfer case, and 2 high up in the transfer case.

When testing them, you have to use a multimeter testing for continuity thru the full range of the switch. If there are any dead spots the switch needs cleaned or replaced, not just at full in or out.

If you read the big blinking 4wd thread from 99SC, you can find the diagram of how the sensors need to function. If any of those read out of phase the system doesn’t work.

Next you have to check the actuator contacts on the transfer case. Inside there are contact trails that need to be corrosion free so the actuator gets power. Check my build thread, I have some pictures of the guys of the actuator.

 

It sounds to me like you lost either power or ground to the 4wd ecu. The 4wd ecu delivers all of the switched circuits to the actuators, switches, VSVs, and indicator lights. At the 4wd ecu there should be a blk/ylw wire that should be battery voltage with key on. Should also be a wht/blk wire that provides ground at all times. The ground for the 4wd ecu comes from the driver side kick panel. I'd start by checking power and ground at the 4wd ecu.

 

My man!! Exactly what (I didn’t know) I was looking for.

 

Damn. Didn’t think to check for continuity while I had two of the switches out. Good to know!

 

Now that I remember, my negative battery terminal came off while I was wheeling and that’s around the time that my 4x4 light went off.

I hooked my terminal back up of course - however I wonder if disconnecting my negative terminal mid-wheeling session could affect the 4wd ECU? There is of course the possibility of a simply loose ground on the 4wd ECU just from a bunch of harsh riding.

 

Sorry, I'm late to the party. You have gotten a lot of good advice. One thing strikes me:

So, two things are out of whack here. You are getting vacuum on one side only, and it stays that way, regardless of input. Meanwhile, you have zero electrical signal on either side. First, you should get an electrical signal on one side or the other unless the system is unpowered or the ECU took a dump. Two, you should not get ANY vacuum on either side if there is no electrical signal. I really doubt you had two sudden, unrelated and simultaneous failures which is what is needed to create this symptom set.

Sorry, but this leads me to suspect you are reporting bad data. First, unplug both leads to the VSV and confirm you have vacuum on one side. If you do, that's a bad VSV on that side. If you have no vacuum with both unplugged, then at least one side is good. In either case, we need to revisit how you are testing for signal at the plugs.

I don't see how a position switch could cause this symptom set. The ECU will always send a signal to one side or the other, unless something is VERY wrong. A bad position switch can't cause it to send NO signal, only the wrong signal. Even if the cycle does not complete, it won't give up...it will still send one signal or the other.

EDIT: I read it again. There is another thing that bothers me. You say you can't rotate your front driveshaft in 2wd. This means you are always locked at the diff or locked at the TC, or both. In the last case, you are in 4wd. But you say you never have power to the front. Please try this. swap the vacuum hoses side to side at the VSV. See if you are then able to rotate the front shaft...try each 4H, 4L and 2H. Report back.
We can sort this out, but there is more diagnosis work to do here for this to make sense.

 

I have the exact same problem with my 97 4runner limited. The wires for the power seat on the passenger side shorted out and then e 4wd stopped working. Which makes no sense because the shouldn't be connected, but I tried everything you said and I thought the same thing. I replaced the 4wd ecu and it still didn't fix the problem so I'm thinking there might be something else causing the problem.