flightjunkie

Hey all,

I finally picked up a 1999 4runner with only 85k miles and rear differential locker the other day, knowing the 4x4 wouldn't engage. The physical shift lever will go into all modes but the actuator isn't functioning. I read for hours about the possibilities and bought it hoping it is just a vacuum or sensor issue, not the actuator(s). It seems the general consensus from all the posts from prior years is to check vacuum, then electric. This is the first time I have worked on a car in any depth which is why I am posting some of these very basic questions.

After extensive attempts of freeing the actuators by shifting in all the suggested ways (slow rolls, tapping brakes, sharp turns, drive to reverse exchanges), and tapping the actuators, I started here:

"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.]"

1. After performing the test, I found that both vacuum line nipples had suction, which seems to contradict what the test is supposed to find. The layout of the hoses lead to the same hose running through the check valve (which I tested and is functioning), to the manifold. Am I missreading this or is there an issue with this configuration/the fact both nipples have suction.

2. If it is confirmed my vaccum test is satisfactory, it seems I need to test the actuators, or the ADD sensors (any advice on which to test first). I read "If you pull the plug on the actuator and use 12volt source to see if you have a bad actuator.

With the plug to the actuator in your hand and the lock of the plug in the up position the pins are #'d backwards 321 on the top row and 654 on the bottom. With + on pin 3 and - on pin 2 the DC motor will drive the actuator into 4WD and then +2 and -3 it will go back to 2HI. This will tell you if the actuator motor works or not. If the motor works then you can look other places. "

So my next newb questions are first, am I disconnecting the plug toward the top of the engine bay/solenoids or on the actuator it's self? it I am assuming in the engine bay but I couldn't find that confirmed OR it's location. Second, I can't seem to find how exactly I create a 12 volt source. I have a battery jump pack with a 12 volt plug, could I just use any old 12 volt cord which would plug into one of these and splice the wires for the test?

Thanks a lot for any help or thoughts.

TheDurk

You should not have vacuum on BOTH nipples; it should switch from one to the other as you go from 2wd to 4wd. Anything else, is a problem. The nipples to check are the ones with the long hoses that go down to the actuator on the front diff.

On your rig, '99 limited, you have two actuators, an electric one on the T-case and a vacuum powered one on the front diff (the ADD).

The first thing I'd do in your case, is unplug both VSV's. If either side is still passing vacuum to the ADD with no electric signal, then replace the VSV because one side is bad. Or if you still have vacuum on both sides, then both sides are bad. If it goes away on both sides, you have a weird electrical issue where the 4wd ECU is sending a signal to both sides (never seen this). Post back and we'll attack it.

I'm the guy that wrote that stuff in italics up top. That is all about the front ADD with vacuum actuator. The stuff in 2 applies to the electric actuator on the T-case; don't confuse the two. I did not write that. Worry about the VSV first, it is probably your issue.

flightjunkie

TheDurk

Thank you for clarifying. I just unplugged both electrical connectors to the VSV and removed the hoses, then started truck in 2wd. The front nipple had suction, the back one did not, so based on your thoughts it seems the front VSV is bad. I thought I would include these pics to ensure I am not mistaking the part in question:

http://imgur.com/87QaSQg
The two plugs I disconnected. The blue one is in the back

http://imgur.com/B7eNVDL
The two long hoses (with the tape) running to below the engine. They apparently share a shroud on the way down so I assume they are the right ones.

If you confirm I have not made an error, I will call around to see who has the part. If this is the case and anyone has reference to the part number let me know!

TheDurk

Yeah, that's it. Boy, that is rusted to hell. Could be part of the problem. Are you in the salt zone?

When you see this, you'll realize it's time for a visit to the junkyard or car-part.com:

Toyota Part Number: 85440-35040
SOLENOID ASSY, FOUR WHEEL DRIVE CONTROL

http://www.toyotapartszone.com/oem/t...440-35040.html

So in the meantime, if you need 4wd, unplug that front solenoid hose and stick a golf tee in it, and also unplug the supply line to that side and plug that. Then you should go into 4wd successfully. I'd do that as your final test that all is otherwise ok.

In fact, you can control the ADD manually by connecting 2wd hose to the bad VSV (that has full-time vacuum) and plugging the 4wd hose. When you want 4wd, put the 4wd hose on the bad VSV and plug the 2wd hose. Also plug the supply to the good one so you don't lose vacuum when that solenoid opens.

Since you have nothing to lose, you can try spraying WD40 down the pipe of the sick VSV, then whacking it against the wall a few times, rinse and repeat. Blasting the crud out with compressed air might help, too. You never know...just don't expect it to last if it works. If you have a DMM, you can check the resistance of the bad solenoid. If off spec, it's a lost cause, save your WD40. Spec for that is 37-47Ω.

flightjunkie

Durk

Yes the car came from the rust belt, there are a lot of components with moderate rust

Unfortunately, after your last suggestions it still won't go into 4wd (indicator lights still continuously blinking after trying everything again). I suspect the actuators have not been activated in far too long and fear the worst.

So it now seems the VSV is bad, along with at least one other component. Is the next logical thing to test the actuator/front differential sensor?

Just ordered these, looks like I will need to acquire a new bracket to mount them on.

http://www.ebay.com/itm/141455296572?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

TheDurk

You're probably right.

If I were you, I'd put it up in the air--all 4 wheels, then engage 4wd including applying vacuum to 4wd hose and see if front propeller shaft is turning. If it is not, issue is in T-case actuator. If it is, but front wheels don't turn, then issue is front diff actuator. Until you know which to attack with certainty, you can't make progress.

Oh, and if you can turn the shaft by hand when 4wd is engaged, then NEITHER is working. Then start with the T-case actuator as that is first in the chain.

flightjunkie

Can you confirm the front propeller shaft is another term for front drive shaft?

TheDurk

Yeah, that's what Toyota calls them.

flightjunkie

Durk

I thank you again for the assistance. The VSV's came in and I swapped them out which resolved the issue! Not sure why the test wasn't allowing me to get 4wd to engage manually but that's irrelevant now.

I drove around in 4wd a decent amount, and shifted through the modes to get everything moving and lubed.

One anomaly is the rear diff locker light is on in any 4wd mode, but not 2wd (the 4wd lights work correctly otherwise). From my understanding the locker should only engage in 4wd lo. Any thoughts?

TheDurk

Please clarify: RR DIFF LOCK light comes on in any 4wd mode whether or not diff lock switch is on, or only when switch is on?

From the circuit, Diff Lock should engage only when L4 Detection Switch is on and speed is under 5mph. So I suggest you check the L4 Detection switch on the T/C. It is the one with the BLUE connector housing. The others should be gray. It should have continuity when depressed, otherwise open. I'm thinking it is stuck in the ON position. Sorry, it is a bit of a pain to get to. So you might prefer to check that Pin 8 of Plug D29 (Blue wire with red stripe) on the Diff Lock ECU in Driver's Side kick panel gives ground only when L4 is engaged. That should be the only Blue-red wire on there.

I'm not familiar with those puppies (really wish I had one), so I can't think of anything else looking at the EWD.

Do people hack these things to allow 4H use of the Diff Lock? Like for snow? Grounding that Pin 8 would do that. Not sure if that would freak out the 4wd ECU though.

Oh yeah, you're welcome!

flightjunkie

RR DIFF LOCK light comes on in any 4wd mode whether or not diff lock switch is on.

I will perform the test later today. I'm assuming I shouldn't drive in 4wd until this is resolved since the locker is only designed for low speeds?

TheDurk

Yeah.

Can you tell from the way it drives if Diff Lock is truly engaged? It would be nice to know for sure.

Given your answer above, I would also check the detection switch that is on the rear diff. That might be the stuck one. More likely, in fact, so check it first. Should be easier to get to. Also has a blue connector. It would be really nice if that was it.

Make your life a little easier...instead of pulling these switches, just unplug their connectors in turn (while in 4wd) and see if the light goes out. If one does, THEN pull it, check the switch and try to clean/lube it up. You should be able to reach the blue connector on the T/C through the shifter hole if you can't get to it from the bottom.

If neither of those is the problem, time to rule out that the locker is engaged full-time. If you jack up the rear, and spin one wheel, the other should go the same direction if it is, and opposite if it is not...I think. If I'm wrong, hopefully some locker expert will correct me. Electric is my strong point.

flightjunkie

Okay, I was misleading about something. When in 2wd and I press the digital "4wd" button (as others point out, it should be labeled AWD) the 4 green lights come on but not the orange rear locker light. So AWD is working properly from my understanding. It's any mode of 4wd using the lever that causes the the rear diff light to glow orange, regardless of if the rear locker switch is engaged or not.

In 4wd modes (using the lever), it sure feels like the rear dif is locked when I turn and the tires bing. But then again, I feel the same phenomena in ford trucks I've driven in 4wd. So I guess the only way to confirm is jack it up and spin the wheels.

TheDurk

Gotya.

Well, if you can identify a bad detection switch then that might resolve the matter. Otherwise, we need to be positive whether it is really engaging the locker when it's not called for or if the ECU just THINKS it's engaged.