I hate to make three posts in a row but I fixed my issue. When I gave up yesterday I had manually shifted both my TC and ADD to 2WD using a battery, relay and some test leads then left the ADD connector loose to keep it out of lock in the event that I had an emergency and needed to drive it. I still had the blink. Today I removed both sensors above the TC actuator and checked their continuity while I worked them by hand. Both had continuity. I went a step further and firmly attached my leads and ran the test while slowly working each switch to it's limit and found some irregularity in the forward most switch especially when I pressed it in to the limit. My meter's tone would stop very briefly during the stroke and would almost always stop at the limit. I cleaned the switch well while working it and the tone became steady through the stroke. I reinstalled the switch.

I started the truck and the same flashing light. I decided to reinstall the connector to the front end and double check before starting over on a ECM test. Guess what? I had full control again. I may not have permanently solved the problem but I know where to look if it does it again. I will simply replace the sensor the next time it happens. It took me a while to find it but I have a much better idea of how the system works and that's worth something to me.

 

Thats killer. I can only hope it is something that is relatively mild labor-wise.

I know the front is engaged. I am hoping to check the switches on top just to be thorough, then jump that front ADD actuator as you suggested. Today I was able to get some of the tiny speaker terminals which should help immensely. Thank you for the the suggestion on that.

I wish I could find a definitive easily explained "order" within the electrical actuation system. That would make trouble shooting the future somewhat easier.

 

[QUOTE=i
I wish I could find a definitive easily explained "order" within the electrical actuation system. That would make trouble shooting the future somewhat easier.[/QUOTE]

I don't know where to find it. Here is my theory on it. Someone please correct me if I'm wrong and I'll delete the wrong information.
1.Push the button. Signal sent to ECM
2.ECM sends signal to both actuators.
3.The 4WD position sensor at the TC sends signal saying I'm in, Front actuator sends signal saying I tried to go in. (No switch on the newer ones. Only a change in continuity between two pins on the connector but adequate to send data back to ECM.)
4. If all that happens together, the ECM blesses the shift and lights up your dash indicator. If any one piece of data doesn't make it back to the ECM, you get the blink.

I think the highest priority feedback the ECM gets is the 4WD position sensor. When I was shifting mine using the relay on the TC actuator, if I made a change, pulled the 4WD fuse and then replaced it before cranking, I think I remember the front actuating to match. I know it would work if I shifted it to 4WD with the front end unlocked, pulled the fuse, pressed the button and then replaced the fuse. It would wake up locked in 4WD with the dash indicator green and ready. This would only happen when manually actuated it to match what the position switch was saying. Any other position I put it in would cause a conflict and the ECM would give it thumbs down and blink. That's why I think that the signals from the TC can override whatever signal the ADD sends if it even actually does send one.

I wouldn't get in to those upper transmission switches unless I had tried everything else first. They should be your low range and neutral position switches and are part of the transmission circuit and, I don't think, have little to do with what you are working on.

Again, this is only my theory on it. I haven't seen any kind of explanation out there in my searches. Please correct me if I'm wrong.

 

Im happy to reply about my issue with the blinking lights that we all hate to see and in my case i had to replace my transfer case the whole unit had to be replace and now i got 4wheel drive again!!!!!

 

I am seeing exactly the same symptoms as OP (99 4R Limited 245K). Rained a little so I wanted to go into full-time and it never completely went in and would not come out. Stuck in 4H-locked with blinking indicator. Apply the switch and it just keeps blinking. Turn it off and it stops blinking for 3 secs then starts blinking again.
Dealer had to order the front diff switch part (for the full $60, I might add) and I just crawled under and got it out of 4x4 with 12VDC so I can at least drive it before I get it installed/install it.
Actuator sounds fine in both directions so that's good.
Thank you all.

 

1999 Limited:

I initially had this problem when I got mine in November 2015, and jumped the 4wd actuator only to find out the actuator rotary switch was out of time. This must have been done by the previous owner when the issue arose, not sure. Removing the gear and through the process of elimination, I got the actuator re-timed to where it was hitting the setting properly for each 4wd/AWD position. Jumping the actuator may cause it to overrun it's range of motion, even though there is a tab inside that seems to be a stop, which might be fine if the motor runs quickly during disengagement. The loaded spring may allow it to jump over that tab when jumping the connector for too long of a duration...The problem was resolved. Then, during this summer, I had an issue when engaging the 4wd lever. The front axle was not engaging the ADD, although I could get the locker to engage in low range, which got me through the slightly slippery climbs on the trail. After going through the steps of checking everything again, I pulled vacuum on each of the hoses on the ADD actuator on the front axle to find that the ADD could actuate. Luckily that meant there was not enough vacuum to engage the front ADD clutch as designed. I started pulling vacuum hoses in the engine bay only to find out that 5 were cracked. After changing out the hoses, the system engages and disengages flawlessly and very quickly. Keep in mind that these vehicles are rather old and rubber may be dry rotted in certain places. Since rubber hose is cheap, I would recommend that everyone replace those before moving on the mechanical failures. It simply cannot hurt.

 

That's some good troubleshooting on that gear timing in the actuator. I would have never taken it that far. All of the 3rd gen 4runners I have owned have had electronic ADD actuators but I recently parted out a 2000 model with the vacuum actuator. In doing so I surely recognized the potential for vacuum leaks due to cracked lines. The lines on that one were very hard and brittle at the actuator. You are exactly right about replacing them before getting too deep into any mechanical troubleshooting. When someone needs help with a cranking issue, I will hardly get into in too deep with them before they have verified that the battery is up to spec and won't dive into a fuel delivery issue until the fuel filter is changed. Things like these are maintenance items and are money/time well spent to test/replace, even if they aren't the root cause of the issue.

 

Hi,
I have a 2000 4runner Limited 4WD. My 4wd will no engage. Lights just blink.
- In the process of testing all of the position sensors. (Already replaced 2 bad ones still no 4wd). I have one left to test.
- I have been able to test the front diff sensor, the two on the very rear of the TC, and the two on top of the TC drivers side.
- There is one last sensor I have not been to able to take off or access. The position sensor on top of the TC on the Passengers side.

I have a separate thread going with Durk helping me, but I am specifically looking for some advice on how to get that one sensor on the passenger side off without having to drop diff/tranny?

Thanks!

 

Disregard previous post. I was able to remove it!
If anyone else needs to test this one use a 12" long 1-1/16 combination wrench. Insert the sensor wire connection through the open/circular end of the wrench and slide it all the way until it grabs the sensor. You will have very limited space, but enough to pull down on the wrench and loosen it!

 

I can help. Where is your other thread?

 

Hi Charchee,
Here is a link to my other thread:
https://www.yotatech.com/forums/f2/2...er-vsv-298101/

My issue is that my 4WD will NOT engage. 4WD light stays blinking.
I have 2000 4runner Limited 4wd.

With the help of Durk I have been running some test. As Durk always suggests we start our trouble shooting steps at the Vaccum Switching Valves.

- 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.

From my understanding we must first verify that all switches/sensors are in good working order.
- Tested Front Diff sensor (Failed and Replaced with new sensor)
- Tested TC rear sensors (One Passed. One Failed. Replaced faulty sensor with new one)
- Tested TC Top drivers side sensors (One Passed. One Failed. Replace faulty 4wd Low position sensor)
- Tested TC Top passengers side sensor (Passed)

As this point I think I've tested all my switches/sensors (unless I missed one please let me know)
- I still have no 4wd engagement
- I still have flashing 4wd lights.
- I still have no power going to my 4wd VSV solenoid (the Blue one).

If I understand correctly the ECU reads outputs from all of these sensors, which then sends instructions to power the 4wd VSV solenoid, which then switches the vacuum to this side. I haven't started trouble shooting actuators, because I don't think I'm there yet. I should at least have vacuum in my 4wd VSV ADD solenoid, correct?

My next step was going to be start trouble shooting the 4wd ECU. I'm using the PDF file that has been posted here to inspect the ECU. For some reason my wire harness connector looks nothing like the one in the PDF file. Also the wire numbers do NOT match up. I'm I interpreting the diagram incorrectly, or is this PDF to inspect the 4wd control ECU not for a 2000 Limited model? As you can see in the picture below the top left side green cable reads #13 on top of it. According to the diagram it should read #7. (I disconnected my ECU connector to capture a better pictures of it).




Thanks!
Dan

 

What were the results or your sensor tests. If you haven't figured out your issue yet, let me give you a hint before you put that hard to reach sensor back in. If you are testing them for continuity with a multimeter. Set it to tone so you can hear it, connect the leads to the prongs of the sensor and push in the ball at the end of it. You should hear tone when it is depressed. That much I'm sure you know. The issue that I have seen twice now is that when you push it in very slowly and hear tone, if you keep pushing slowly, you might hear a break in the tone. This break in the tone is a bad spot in the switch's range of travel which is enough to give you a case of the blinks. You can normally clean up the sensor using WD40 or something like that while pressing in the ball repeatedly. Keep working it until you get a clear, solid tone throughout its range of continuity. I went through this twice and both times my preliminary test showed the sensors to be good.

Secondly you can test for continuity while the sensors are still screwed in. You should be able to determine which position the computer thinks the transfer case is in. Once you know this, make sure your front diff is thinking the same thing. A lot of times it won't be and you may have to use a power source or your battery to jump it back into place. If you feel like you have everything where it needs to be, pull the 4WD fuse out of your driver's side kick panel to reset the computer. Replace it after a few seconds and start it up. Since the computer will not assume to know what position it is in, it will look to the position sensors for an answer. If everything matches up in either 2WD or 4WD, your indicator light should either go off or show 4 green wheels.

Not sure where you are in your troubleshooting now but I can walk you through the whole thing in more detail if you need me to. There is a lot more to it than those two tests but won't get into it if you already have it figured out.

 

I've read this whole thread and I'm at the end of my chain.

I've got a '97 Limited, Auto, not the J-shift...that won't go into 4WD. No light, no nada.

I have checked the 4WD fuse with a known good fuse.
I have checked the push button switch on the shifter for continuity when pressed.
I can engage the frontend by reversing the vacuum lines at the VSVs.
I can engage/disengage the T/C actuator with an external power source to pins 2 and 3, reverse polarity to disengage, blah blah...green light and everything works.
When I check pins 2 and 3 on the harness side, I do NOT get 12V.....or any V for that matter, with engine running and 4WD button pressed.
I have replaced both switches on top of the T/C because they tested bad. Switch above the T/C actuator tests good.
I have not tested the switch at the front diff because when I engage 4WD via external power source I get a green dash light and everything is cool.
I have located the 4WD ECM, and have 12V from pins 1-8, but didn't get much past that as I didn't know if I was doing it right by testing the harness without the ECM plugged in, and I don't know how to test it otherwise.


Of everything I've read, nothing mentions the vacuum line on the T/C actuator??? Or is that a vent hose?? It was unplugged when all this started...
I found some instructions that mentioned testing the Vehicle Speed Sensor, but nothing to show me how to test it, or even where it's at on a '97.

Any help would be greatly appreciated gentlemen.

 

On a 99 Limited, when you shift to 4HI without center diff locked, terminal 12 of the ECU will be hot with incoming power from the fuse. Terminal 13 will go hot with signal from the ecu to the actuator. This power should flow to terminal 3 or the actuator, feed back to the ecu through terminal 2 of the actuator. This signal will go back to terminal 26 of the ecu. That signal will come back out terminal 25 of the ecu and go to ground. Clear as mud?

If this info goes for your 97, test the harness side of the ecu connector for power on 12 when you shift to 4HI. If you don't see it there, then your problem is between your shifter and the ECU. If it's there, you're going to have to continue your tests with the plug connected. Not to hard to do. Just probe from the back of the connector. The trick is to make sure you are connecting to the terminal or else you'll get a false negative.

If the issue was with bad feedback or a problem with your front diff, you would be getting the blinking light issue. I think for some reason, you aren't getting a signal from the ecu back to the TC actuator.

I doubt it's an issue with the speed sensor. I think a high speed signal to the ecm will give you the blink and even a buzzer of some kind from the ecu.

You said it wasn't a J pattern transfer case. I didn't know the straight pattern with push button setup was available in 97. What transfer case shift pattern does yours have and does yours have the push button AWD option?

 

The '99 must be different from my '97, my ECM only has 16 terminals and some of those aren't used.

It is a straight pattern T/C, with the push button AWD. The button is the only way to get 4HI. But shifting forward into 4Lo doesn't get me in 4wd right now either.

 

Then you have the same setup as my 2002 except mine is all electric up front.

Try this. Lift up the shift bezel and find the connector for the button. Disconnect it and short the two terminals on the harness side of the connector. I was having an issue with mine a while back. When I tested my switch on the switch side of the connector, I was getting continuity with the button pressed but when I kept pushing the button to replicate the result, I noticed that it worked a time or two and then nothing after a bunch more pushes I got tone again and then nothing again. Shorted the terminals on the harness side and got 4WD. I haven't replaced mine yet. I just ran me two wires to a switch and put it in one of the empty slots in the dash for a temporary fix. Works just fine for now. I need to find me another knob though. I can't imagine what that switch might cost from Toyota. If anyone has one they'd sell, let me know. That probably won't fix your issue but it's easy to test. The fact that you're not getting the blinking light would have me looking at the ECU as your issue if you are actually sending the signal to shift to it.

 

Hi Charchee,
I went back and double checked all 5 of my switches/sensors and all passed the continuity test as you mentioned.
Here were the results from my initial testing:
- Tested Front Diff sensor (Failed and Replaced with new sensor)
- Tested TC rear sensors (One Passed. One Failed. Replaced faulty sensor with new one)
- Tested TC Top drivers side sensors (One Passed. One Failed. Replace faulty 4wd Low position sensor)
- Tested TC Top passengers side sensor (Passed)

I also tried removing the 4wd fuse as suggested. Same results. Still no 4wd. Just flashing lights.
What should be my next trouble shooting step?

I want to test my 4wd ECU, but I don't have the correct diagram for my 2000 Limited. Would you happen to have it?

Thanks,
Dan

 

Jump over to this thread. We're working through some issues on a 99 Limited and TheDurk has a pdf of what you need posted in one of the first few posts on the thread. Should be helpful.
https://www.yotatech.com/forums/f2/2...er-vsv-298101/

 

Update:

With Charchee's and Durk's help I was able to determine that my TC actuator is bad.
- I connected the positive lead from my battery to terminal 2 and negative lead to terminal 3. Actuator fork shaft did not move or make sound.
- I connected the positive lead from my battery to terminal 3 and negative lead to terminal 2. Actuator fork shaft did not move in 4wd or make sound.

I was able to locate a used one at the junkyard and want to try and replace it (they guarantee it is good, so worth a shot before spending $900 at dealer for a new one).
I need some help removing it. I took off the 3 bolts holding it, but it will not come out. Seems like there is a spring inside or something grabbing on to it. Not sure if the rear case cover needs to come off too. Hope not! Someone that has swapped one of these out can you please post some notes? Thanks!

 

Bad news here. I think you have to open up the case to get the snap rings off. Check that last PM I sent you. You have to completely rule out that actuator before you get in any deeper.

He has the J pattern shifter with the button for AWD on it. Does anyone know if he can manually shift the case to 4HI like the SR5s of that age? Also, my 2002 FSM details a method, which I have used several times, for testing the actuator manually with battery power. It asks you to hook up five wires to it via a relay. That's just how I did my test and never actually tried to test it using only two wires. I would imagine this would work to see if the motor is bad but can anyone verify that the two wire test will work?