4x4 Not Engaging - No dash light

[Misfit Runner]

I know I know another 4x4 not working thread. I searched but figuring giving my specifics would aid troubleshooting.

Let me start off by saying I'm new to this forum, Toyotas and off-roading all together. I come from the land of lowered German cars. Love the forum!

I just bought a 99 SR5 3.4L auto less than two months ago. Let's just say it's been fun and I've learned a lot. Once I get the bugs worked out it should be/hoping I'll have a great rig.

It's very cold here the last 2 days -34 Celsius. Have used 4x4 several times since the purchase. Went to engage on the fly today to 4hi and it had a hard time going in. It did not engage at all, no light. Tried messing with it. Stopped and tried it in 4lo. Grinder a bit, was probably nervous and frustrated. Will go into low gear but will not engage front driveline and again no light. Tired it some more driving and stopped, J shifter moves smoothly between 2hi, 4hi, N and 4lo. I can hear like a switch clicking between shifts as well. No grinding or out of place noises

Any help would be greatly appreciated! Less of me freezing my ass off or dealing with 2wd on glare ice

 

[aykalper]

Almost seems like your ADD doesn't work - the front axle disconnect. May have to check vacuum lines that go to it, if it's not actuating. Others will chime in that are much more knowledgeable about the issue, and the ADD.

I came from a world of lowered Hondas not too long ago. Isn't this community so much better ahah?

 

[Misfit Runner]

The relay that is clicking is the one in the passenger side. I'm assuming that the issue is down the system more, at the VSV or actuator.

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[3bears]

I too came form lowered german cars, that and lowered Volvos, and a nice DD Toyota corolla wagon, which I wish I had never sold.
I would bet that its in your vacuum system, I will try to find the thread that
TheDurk helped me with the same issue a few years back.
Mine ended up being a stuck vacuum check valve, again after the Dirk told me how to trouble shoot

 

[3bears]

VSV’s/ADD
Don't guess at it, troubleshoot! Start at the twin VSV's (Vacuum Switching Valves) on the driver fender wall. There are two long vacuum hoses that come up from the diff, one goes to each VSV. Check to see that one of the two hose nipples on the VSV’s has vacuum (engine running, 4WD NOT engaged. If no vacuum either side, check the check valve going to the intake manifold and look for loose hoses or a hole in the reservoir. If there is vacuum going to one hose, then put it in 4WD. See if the vacuum switches to the other hose. If it does, and no 4WD, problem is the diff actuator or the line to the diff. If it does not, then just switch the hoses and you should go into 4WD. This confirms diff is okay. (Mark the hoses first so you know which belongs where!)

OK, switch them back. Then use a test light to see if electrical signal from the TC also switches sides of the VSV. If it does not, problem is the TC, the switch on the TC, or the TC actuator, or its wiring back to the button (last two for non-J shift only). If it does, but the vacuum does not, the problem is the VSV itself.

I start troubleshooting at the VSV's because you can figure out where the trouble is without having to climb under the truck. [None of this applies to '01-'02 which have an electric actuator.]

***********************************

the above info is courtesy of TheDurk in a thread I started years back


I hope that helps, this was back in 2015...title of thread was no 4wd
and a thread I started. NOt sure hwo to link the thread , but I bet you can find it under my name or the title in the search, but you will have to go back a bit....like I said 2015

 

[3bears]

also another issue I had recently with it not working, I had knocked off a vacuum line while doing an oil change, it was at a junction box below the big black vacuum box where a bunch of hoses come together like between the battery and the box and lower.
how I knocked it loose I don't know, 4wd worked the night before, did an oil change, went for a drive, no 4wd, came back retraced my "oil change" and found the hose knocked loose.

also , way back, I don't remember if the light was coming on or off when it was not working. It made all the clicking sounds, like you are hearing.

the vacuum check valve was not cheap, in that thread I believe it tells you the size etc you can get, I could not find the exact replacement without going to Toyota, so I found one at napa, it had one line in , 2 out, and I capped one of them off.
since then I went with Toyota when I was ordering tons of stuff from camelback

 

[Misfit Runner]

Thanks for the help folks. I'll see what I come up with

VSV’s/ADD
Don't guess at it, troubleshoot! Start at the twin VSV's (Vacuum Switching Valves) on the driver fender wall. There are two long vacuum hoses that come up from the diff, one goes to each VSV. Check to see that one of the two hose nipples on the VSV’s has vacuum (engine running, 4WD NOT engaged. If no vacuum either side, check the check valve going to the intake manifold and look for loose hoses or a hole in the reservoir. If there is vacuum going to one hose, then put it in 4WD. See if the vacuum switches to the other hose. If it does, and no 4WD, problem is the diff actuator or the line to the diff. If it does not, then just switch the hoses and you should go into 4WD. This confirms diff is okay. (Mark the hoses first so you know which belongs where!)

OK, switch them back. Then use a test light to see if electrical signal from the TC also switches sides of the VSV. If it does not, problem is the TC, the switch on the TC, or the TC actuator, or its wiring back to the button (last two for non-J shift only). If it does, but the vacuum does not, the problem is the VSV itself.

I start troubleshooting at the VSV's because you can figure out where the trouble is without having to climb under the truck. [None of this applies to '01-'02 which have an electric actuator.]

***********************************

the above info is courtesy of TheDurk in a thread I started years back


I hope that helps, this was back in 2015...title of thread was no 4wd
and a thread I started. NOt sure hwo to link the thread , but I bet you can find it under my name or the title in the search, but you will have to go back a bit....like I said 2015

I found this as well going to troubleshoot tonight

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[rkymtnman]

Had the exact same issue when we put our '98 together - one of the vacuum lines wasn't connected. Popped it back on and all was well.

 

[phattyduck]

Had the exact same issue when we put our '98 together - one of the vacuum lines wasn't connected. Popped it back on and all was well.

Probably something like this.

The relay clicking in the passenger footwell tells you that the switch on the transfer case is working. The relay switches power to the ADD VSV's in the engine bay.

Check the vacuum line off the manifold (comes off the front or the rear, depending on year) that goes to a one-way valve (1/2" dia canister in the vacuum line run), then down to a multi-connector. One line goes to a large vacuum canister in the fender well, the other two outlets go to the two VSVs below the fuse box. Check all those connections.

Here's the canister in the wheel well:

-Charlie

 

[Misfit Runner]

Vacuum lines seem to all be attached, at least from the vantage point at the top. Comes off manifold goes to VSV and canister, which does not appear to have any visual holes. Maybe the blue check valve, VSV itself or something in diff

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[phattyduck]

Did you try driving around a corner? Does the front drive feel like it is engaged? It might just be the ADD position switch that actually turns on the light on the dash.

-Charlie

 

[Misfit Runner]

Most definitely not engaged, lots of snow and ice. Truck is very tail happy

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[Misfit Runner]

The check valve is working

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[phattyduck]

Ok... with the shifter in 4H, verify that the front driveshaft is locked (truck can be off).

Check for 12V on the ADD VSV connectors. One should have power and the other should be off. Verify that they swap when the shifter is moved from 2H to 4H - the truck will need to be on for this test.

-Charlie

 

[Misfit Runner]

Ok... with the shifter in 4H, verify that the front driveshaft is locked (truck can be off).

Check for 12V on the ADD VSV connectors. One should have power and the other should be off. Verify that they swap when the shifter is moved from 2H to 4H - the truck will need to be on for this test.

-Charlie

Checked VSVs they are switching vacuum properly. Will check driveshaft tomorrow. Narrowing things down at least lol. Must be the actuator or line to it.

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[phattyduck]

Checked VSVs they are switching vacuum properly. Will check driveshaft tomorrow. Narrowing things down at least lol. Must be the actuator or line to it.

That's what it sounds like.

It isn't just the ADD switch since you aren't getting any 4WD. That pretty much leaves the vacuum lines right at the actuator or the actuator itself.

Here's the best pic I have of the front diff out of the truck:

-Charlie

 

[TexasAggie91]

I realize this thread is several years old, but I'm experiencing similar symptoms with my recently acquired '99 Limited and I can't start a new thread. My 4WD doesn't engage and no 4WD dash lights come on when I push the 4WD button on the J-shifter, or when I put the shifter in the 4WH or 4WL positions. I have vacuum to both the VSV valves no matter what position the 4WD button or J-shifter are in, but do not have vacuum from either VSV to the actuator. I also do not have any voltage to either of the VSVs under any scenario and do not hear any relay click when I try to engage the 4WD. I've checked the 4WD ADD fuse with a multimeter and it checked good. All of this leads me to believe I either have a bad ADD relay or bad wiring to the relay. I have located the ADD relay under the glove box but wasn't sure what to do next as far as troubleshooting. I didn't see any obvious wiring issues, so should I just replace the relay and see if that fixes it? I don't mind spending money if it's the right move, but would prefer not to just throw parts at it until I've properly diagnosed it.

PS - thanks in advance for any assistance. This forum has been immensely helpful in getting my 4Runner into shape after it sat mostly idle for the last 8 years by the prior owner.

 

[TexasAggie91]

Did some additional testing today by applying jumper wires to the blue rear VSV to get 12V power to it. Heard the VSV click and measured about 20 inches of vacuum at the actuator with the engine running. Reconnected the vacuum line to the front diff actuator and jacked up the front so that the passenger side wheel was off the ground. Confirmed that the front wheel could not be turned by hand with the blue VSV getting 12V, so it appears the actuator is working on the front differential when it gets vacuum from the blue VSV. Engaged the 4WD button and moved the transfer case lever to 4H but did not have any dash lights come on to indicate 4WD (i.e. neither the green lights for the wheels or the orange light for the center diff came on). When I removed power to the blue VSV, the front wheel was still locked, so I applied jumper power to the red VSV and the front wheel was then free to spin.

At this point I'm pretty confident the issue is in the electrical side of the system, but not sure exactly where to begin troubleshooting that portion.

Based on this thread, 2000 4runner 4wd Limited No Power to VSV - YotaTech Forums
I think there is a 4WD ECU in the driver side kick panel, a relay under the glove box and several switches throughout the system. It doesn't appear the symptoms in that thread exactly match mine (i.e. no dash lights at all for me) and there wasn't a final resolution given in that example. If anyone has suggestions on troubleshooting the electrical side, I'd love to hear them. Thanks again for any help.

 

[phattyduck]

recently acquired '99 Limited .... I have located the ADD relay under the glove box but wasn't sure what to do next as far as troubleshooting.

There is no ADD relay in the passenger footwell on a '99 Limited. The ADD VSVs and transfer case actuator motor are driven/controlled by the 4WD ECU located behind the driver's side kick panel (opposite side from the ADD relay on base/SR5 models).

If you really do have an ADD relay, there is some frankenstein stuff going on that you need to figure out.

-Charlie

 

[TexasAggie91]

Charlie - thanks very much for the reply. I forgot the '99 Limited was different than the other '99 models, so I'm pretty sure I don't have a relay by the glove box. I was basing that assumption on some internet discussion of other '99 4WD systems (and my limited looking under the glove box). I acquired this from the estate of a neighbor who lived across the street from me. She was the original owner and other than routine maintenance I'm sure she never did any modifications. So it sounds like I need to pull the driver side kick panel off and take a look at the ECU there.