dpin78

Hi,
My name is Daniel. Newbie here on yotatech Got a 2000 4runner Limited 4WD.

Issue:
- 4WD not engaging

Symptoms:
- 4wd push button does not light up 4wd indicator lights
- 4wd doesn't engage on 4wd hi or light up 4wd indicator lights
- 4wd engages ONLY on 4wd low (also no 4wd indicator lights)

Troubleshooting:
- Tested 4wd push button. Continuity test passed.
- Checked vacuum lines going from manifold to VSV. Vacuum was good.
- Checked vacuum line going to reserve tank. Vacuum was good.
- Checked vacuum lines going down to the TC. Lines where in good shape, but NO vacuum!
- Unplugged vacuum lines going from VSV down to TC, but no air pressure coming out of VSV!
- Manually powered the VSV's while vehicle ON and both operated as should. I heard the air pushing out of the valves.
- Placed volt meter to both power plugs of the VSV and neither has power.

For now I seem understand why my 4wd is not engaging (no power to vsv).
This is as far as I got tonight.

From what I have read in several posts when the selector lever on the transfer case if moved into 4HI or 4LOW it trips a switch, which then supplies the power to the VSV. Then then that applies vacuum to the vacuum motor on the diff, the vacuum motor slides a slip collar into position locking the two shafts together on the passenger side of the diff, which then trips another switch that illuminates the dash lights and we have 4 wheel drive that we love so much! Based on my trouble shooting I believe my issue is at the first switch that is triggered by the selector lever, which is supposed to send power to the VSV.

I'm a newbie, but thanks to all of the knowledge base on this site I've been able get a small understanding on how the 4wd works on my truck, or at least how it should be working on my truck.
Before I go spending money on sensors, I would like more clarification as to what switch (or switches) exactly get triggered by the selector lever. I've been reading a lot that the TC indicator switch is a common culprit of many 4wd issues. I've seen it referenced a lot when it comes to the opposite of my issue i.e. the 4wd indicator lights don't stop blinking and 4wd does not disengage. Could this sensor also be the culprit of the opposite problem i.e. 4wd not engaging and my 4wd indicator lights not lighting up?

Thanks in advanced!

TheDurk

Did you check the 4WD fuse by driver's knee? Sounds like the ADD system is totally without power. Those switches will usually leave power to the 2WD side of the VSV so I don't suspect them in your case.

dpin78

Yes sir, forgot to mention that. I did verify that the 4wd fuse is good. Any other ideas of why I have zero power? Thanks!

dpin78

Where is the 4wd ecu located?
Want to check everything is good there. Thanks

TheDurk

Honestly, no, but I know what to do next.

Forgive me, but I do this a lot. HOW did you verify that fuse? Please don't tell me you "looked at it." Need to check with a meter, test light, or known good fuse. You sound like you know better, but I waste a lot of time when people don't know how to check fuses.

Assuming it really is good, and assuming you don't hear the TC actuator move either when you push the button, It's time to access the 4wd ECU PLUG in the driver kickpanel and start checking connections.

You need to check you have
-12V between pin 12 (black-white wire) and ground w/key on
-continuity between 25 (white-black wire) and ground
-12V between Pin 23 (green-red wire) and ground in 2wd

Those results will tell us what to do next. here is the EWD from my paper '99 EWD manual. Should be the same as 2000. You can see the pin-outs of that ECU plug on Plug F7, circled near the end.

dpin78

Hi Durk,
Found the 4wd ECU in the driver kickpanel and well.... IT WAS Disconnected! lol

Correct, fuse was tested with meter.

Now I have the flashing lights and 4wd drive not engaging, and this somehow makes me happy because now at least I can trouble shoot the problem.
I own a small dealership here in Texas and bought her at the auction, so I have no previous owner to ask questions too. I guess he didn't mind not having the 4wd not working and figured he would just disconnect the 4wd ECU to get rid of the lights.
But now we know a bad or disconnected 4wd ECU will disable all power to the ADD system. I'll updated my post once I fix it. Hopefully just the infamous TC position switch.

dpin78

Quick update:
Followed your trouble shooting quick guide: (It's all over the forum, but I copied it below just in case for anyone else to see)
__________________________________________________ ____________
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.
__________________________________________________ _______________

My results:
- Engine running and in 2wd position: Vacuum only from Brown (2WD) ADD Solenoid.
- Engine running and in 4wd position: Vacuum stays in Brown ADD Solenoid. No power to Blue (4WD) ADD Solenoid.
- Swapped vacuum line and still did not go into 4WD. Possible bad diff actuator if I understand your notes correctly.

- Switched them back. Used test light to see if electrical signal switched from Brown plug (2WD) to Blue plug (4WD). Engaged the 4wd and power stayed in the Brown plug. Never switched to the Blue plug.

From what I can gather from my troubleshooting so far is a possible bad diff actuator and also a problem on the TC, the switch the TC, or the TC actuator.

I think the easiest thing to test next will be my TC position sensor/switch, which also seems to be a major culprit of the blinking lights.

dpin78

Update:

- Tested front diff actuator engagement switch. Result: PASS (Good continuity)
- Tested both transfer case switches. I found one was bad (The one that uses the same plug as the front diff actuator switch). I went down to Auto Zone and they had them in stock for $41.00.

Still no power to Blue solenoid. 4wd lights continue blinking and no 4wd engagement as expected. Getting there little by little.

Durk, what other sensors/switches should I verify that would send power to my 4wd VSV solenoid?

dpin78

Sorry, TC has 4 switches to test. I only tested the two in the back easy to remove ones. I'll get the two on top tomorrow and update.
So if I'm correct, I have a total of 5 switches to verify?

TheDurk

Thanks for clearing that up. I knew that system was totally dead for some reason.

I don't know that multi-mode that well, or at all really, but I see 6 detection switches in the circuit. One may be on the trans (Shift Lock detection Sw.)

dpin78

UPDATE:
I was able to remove the upper two position switches of the transfer case. Like everyone says space is very limited up there.
How I did it: I went to harbor freight and bought for $39.99 the Oxygen Sensor and Diesel Injector socket set (image attached). Inside of it you will find a 27mm socket with enough room for you to slide the connector through it. The socket is a tad bit long, but if you push it tight it grabs enough of the sensor for you to twist and remove it. For the L4 (blue) connector I had to use a small 1/4 inch ratchet with a 1/2 inch adapter for the socket. For the Neutral position switch space gets even tighter. I had to use a 1/2 inch swivel adapter and a 12 inch extension to give me the necessary leverage needed to get it off.

Once I got them off the L4 position switch has no continuity. So I think I found another BAD switch to replace. The neutral position switch had good continuity.
Below is a pictures of the socket set I purchased and the L4 position switch I need to go order tomorrow. I'll call the dealer, but if anyone has the part number handy it would help!

Thanks!
Daniel

dpin78

I think I found the part number. It should be 84222-35110.

Charchee

I think what I would do at this point is try and figure out which switch on the TC actuator is the 4WD position sensor/switch. Check for continuity with it screwed into the actuator. It should verify the actual state of your transfer case (4WD HI or 2WD HI). With that knowledge, remove the 4WD fuse and apply vacuum to the ADD actuator in order to manually shift it into the matching position. You will also need to shift your TC lever/button to the correct position. I just remembered what the other sensor/switch is. It should be for center diff lock/unlock. Test it's continuity as well. This will tell you whether or not you need the lever pulled to the 4HI Lock position or if you need to just have the button pushed for 4HI Unlocked. Anyway, what you are doing is getting every component of the system shifted to a legitimate shift option. This should resolve any conflicts in the ECM. After everything matches, replace the 4WD fuse and see what your lights do. They should either go out or go solid green depending on the position you have it shifted to. When you have a conflict in the ECM, which cannot think dynamically and make a decision outside of it's logic, it will remain in a state of confusion and will halt any further action in the system, giving you the unending blinking light condition. By setting it all back to an acceptable scenario, the blinking should stop.

At this point the next step is to try and shift it again while watching for a signal to the VSV. If the lights go back to blinking and you see no signal to the VSV, your issue is likely with the ECM. If the lights go to blinking and you did see signal going to the VSV, then your issue is either with the VSV or the ADD actuator. However, if you were able to shift the ADD by applying vacuum manually, it's not likely that your actuator is bad.

I'm sorry I can't give you specifics on the continuity readings you should be seeing on the two switches. I can try and look them up in my FSM but it may be different than yours due to the differences in the 2000 and 2001 4WD packages. I'll look them up anyway and post them.

Charchee

Do you have a flat 6 pin connector on your transfer case actuator? If so then it is like mine and I can tell you what pins to test in order to tell you what mode your transfer case is reporting to the ECM.

Durk, how did you post that PDF? Do you attach it just like a picture?

dpin78

From the diagram I attached below the 4WD position sensor/switch is located on the rear of the TC. There are two of them. It's the on towards the front of the car.
- Continuity checked on the 4WD position sensor: NO Continuity, which means state = 2WD correct?

I removed the 4wd fuse and applied direct vacuum to the 4WD (Blue) Add actuator.
- Placed the TC lever into H4 Lock position.
- Replaced the 4WD fuse
- Lights still blinking.
- I tried the same with just the button pushed for 4HI Unlocked. Lights still blinking.
- Power/Signal never shifted the VSV 4WD side. Only Constant power to the 2WD side.

I also ran some tests on my 4WD ECU. When I engaged the TC lever into H4 or use the 4WD push button 4HI unlocked I should have voltage on wire/terminal # 10.
The ECU is not sending a signal to terminal 10, which is what sends the power to my VSV 4WD solenoid.

Could I have a bad ECU?