I do have a 99 4Runner Limited M/M 4wd ECU and a brand new Toyota # 84222-35110 sensor/switch for sale, if anybody needs them.

 

I've been a long time reader. My 1999 4Runner Ltd 4wd has been problematic for a few years. But lately it has been stuck in 2wd, and I live in a snowy area... so driving rear wheel drive has been terrible.

Long story short, my problem appears to be related to the vacuum switches up near the battery. The 2 vacuum lines that run down to the front actuator. I wasn't getting any suction at the actuator, so I traced the lines up to the engine. They connected to 2 switch/sensor type things right below/next to my battery. Then there was a vacuum tube line that ran into my engine to generate the suction when the car was running.

Well I found I could simply override the bad vacuum sensors/switches by moving some tubes around. I bypassed the bad sensor and kept the vacuum on 100% of the time for one of the lines (to engage the front axle/4wd). And then I took the small piece of hose I removed and used it to close off the other sensor valves (a closed loop if you will).

My truck instantly popped into 4wd, and I'm able to switch between all-time 4wd (4H), 4HL, and 4L. Now granted, I cannot switch OUT of 4WD at this time... but that is fine by me!

Come summer I plan to simply switch the vacuum hoses around and disengage the front axle. That, or I may look online to buy some used vacuum sensors and try to swap mine out. They both seem to be broke. I saw some online on ebay for like $30 bucks each.

But not worrying about that for now! I'm back in 4wd action! =)

Thanks again everyone!

 

How do you know they are 'broke'? Have you read this thread at all?

 

Hey Durk. Nice to meet you sir.

I'm guessing the problem is with my sensors up near the battery. It is just a guess based on my tests to the vacuum line. With the car running and trying to engage/disengage the 4wd, I was not getting any vacuum at the front actuator (I pulled the hoses off and felt/listened for any suction).

So then I followed the lines up to the engine below the battery. There I pull the hoses off the sensors and no vacuum/suction was coming out either sensor. I then pulled the hoses off the other side of the sensor (the line that runs to the engine). Then I finally found a strong suction/vacuum. So I figured the vacuum part was working, it just was not getting past the sensor/switch.

Maybe those sensors just need to be cleaned, or something, or maybe there is an electrical issue that controls those sensors, but I decided to just bypass the the engaging sensor since I am happy to have it be in AWD all the time anyway at this stage in my truck's life... and our weather warrants AWD (4H) most the year any way.

Plus I'm not convinced I don't have a 2nd problem in the rear actuator. I think that one may be stuck as well, since when I was stuck in 2wd, the front transfer axle/whatever... was locked... which I'm thinking was not right for 2wd... it should spin free from what I've read...

To summarize, I don't know for sure what is broke, but I was able to bypass a potential problem area to get my truck working in 4wd again...

PS - I did also swap out a front switch above the vacuum actuator... but I tested the old one with a multimeter and it seemed fine... but since I had a new toyota one I put it in anyway...thinking that switch may go bad soon since it seems to be a common issue. I kept the old one in case I needed it. Swapping the switch alone did not help my specific problem.

 

I have read all 22 pages and can't find anyone with the same issue.

2000 SR5 3.4L Manual Transmission, Manual 4 wheel drive shift- no button

I have no blinking lights at all (it's not the fuse, I checked) when I shift to 4H or 4L and she remains in 2WD. I can put the manual 4WD shift lever to Neutral though and it takes 2WD off.

Worked just find the last time I engaged, which was about 6 months ago. Any suggestions?

 

This may help some of you guys with the 2001-2002 models with push button 4WD. I recently had this problem and this is what I found.

https://www.youtube.com/watch?v=T1Zb...ature=youtu.be

[YOUTUBE]T1ZbLxFTrH4[/YOUTUBE]

 

I've read through the thread put did not see my problem similar but not the same.

I ran over a metal rod off road putting a hole in oil pan blowing engine. ordered an awesome replacement from japan with only 47k, truck has 157k, anyway just got her back from the shop. I normally would have swapped engine myself but did not have time and hate working in the winter on my car's lol. yep I'm a wussy in the winter.

Anyway, when I used the push button on the fly 4x4 mode light works as it should on and off. When I manually shift into 4x4 high or low I'm getting no lights at all. Yes! I know I can bring it back and have them deal with it. but it's a busy shop and they had it for 2 months and I would rather just crawl under her and fix the problem then drop it off for who knows how many days. Since my issue does not have any of the same symptoms as the issue's I'm reading in this thread I thought I would ask for advice before I crawl under her. The issues I'm reading mostly is the light on all the time or off all the time, blinking or not engaging. My 4x4 system seems to be engaging and working fine and light working correctly with on the fly button but, no light at all with manual 4wheel high or low.

 

I read through this whole thread over the course of a few days. Still need some guidance. I apologize if my specific issue has been covered already.

I bought my 99 Limited auto with 194k back in January. Up until a few days ago, the 4wd system worked without issue. Few days ago, when trying to engage AWD, I got the blinky 4wd death lights. Here is what I have done. Removed and tested continuity in the front diff switch/sensor, the two switches that I could get to on top of the TC. All 3 tested fine. I checked out the VSV, determined the unit was getting vacuum past the check valve, and checked the fuse. With the button off, and the lights blinking, the front driveshaft was locked, as I suspected. I think the system got itself into 4 at some point when the light was flashing. I did the vacuum switch trick to get the system back into 2, and tested the front driveshaft. It rotated freely. Reversed the lines and the front driveshaft locked again. So the actuator on the front axle is good. For right now I have the lines oriented in such a way that it's in 2, which is what I want for now. I think the lines are backward from where they should be. So this tells me that either the VSV is bad, or is getting bad/no information from the TC. This is where I'm stuck. I could use direction on the next steps, please. Thanks!

 

Wait a tick. That cover can be pulled without ill effect? Is it the component underneath that can't be removed without the headache of catching springs and realigning?

 

Did some probing and discovered that the blue connector at the VSV (puts front diff in 4wd) has power all the time. No matter the status of the AWD button or the position of the 4wd shifter. The brown connector never gets power.

On my very short test drive I couldn't get it into 4HL.

 

Update: changed the TC fluid and everything is back to working order. For now.

 

I am having similar issues with my 99Runner Ltd, can anyone tell me how difficult it is to access the Blue ADD solenoid and the Brown ADD solenoid?


Are these on the top of the transfercase? Best approach?


I figure spending the money to replace both switches as well as the front diff switch isn't a bad idea since I have about 200k on this truck.


Thank you guys for all the great insight!!

 

They are on the driver side fenderwall, just aft of the battery. Easy to access.

 

So everyone's prob is a lil different it seems. My 1997 4Runner LTD push button AWD and rearlocker switch will not engage in 4WD. (no green lights on dash, output shaft from T/C free wheeling) I started with checking the VSV's, one had vacuum, one did not. Actuated the 4wd button on the TC lever, no change. The same VSV had vacuum, the other did not. Swapped the vacuum lines going down to the ADD, it had engaged, as the front wheels were on a ramp and I could not spin the output shaft coming from the T/C. I removed the connector going to the T/C motor and jumped pins 2 & 3 with power off the battery (jumper cables to #13 wire with alligator clips, no 2 amp protection (bad idea?) Any way, I could hear the actuator move both ways, sounded a little binding at the end going into 4wd. I thought great, it's working, maybe just a little binding from no use. Got in, went for a drive. Now, all 4 green light are on, and it's stuck in 4WD, no flashing lights, all steady green. Actuated the 4wd switch on T/C lever numerous times, in park, in neutral, while driving, while reversing no luck-stuck in 4wd, all steady green. I actuated the RR diff lock switch below in the blinker, while 4H i would get a flashing red diff lock on the display, and in 4L it would go steady red, and the ABS light would come on. So Durk, where do I start? sensor switches or the 4WD ECU? where is it located, any Idea?

 

A little handicapped because '97 is the one year for which I do not have EWD's. I'm guessing it's like '98 and the 4wd ECU is in driver's kick panel, but no guarantee.

As to which is the cause, I still would not rule out the T/C actuator. You should probably try to jump it back out of 4wd to make sure its not locked up. You also need to rule out the 4wd switch on the T/C shifter. See if that signal gets to the 4wd ECU.

I don't think I could do this one over the internet as to finding a cause. Hands on, checking various points, I'm sure I'd get it eventually.

In your position, I'd check that button, then those detection switches. The 4wd ECU are rarely the culprit, and those detection switches are dropping like flies. Since they are a common fail, and a cheap fix relative to actuator or ECU, I'd check each one for continuity. If they're all good, then find someone knowledgeable to troubleshoot the thing.

I do have the 4wd schematic for '97 Pushbutton but nothing else. Attached below.

A dealer would probably check the switches, then swap the 4wd ECU, then swap the actuator. They are good at swapping stuff. $$$

 

I did jump the Pins at the T/C a few times, when I had the connector off, it seems to move a little better each time. I think i moved 3-4 times each way. As far as the switch on the T/C lever, I removed the connector and just jumped it with a wire, nothing happened. That was the second thing I did after swapping suction lines off the VSV's. So now I guess it's time to clean/check continuity on sensors, 1 on the front differential, and 4 on the T/C? How are guys getting those 2 on the top of the T/C off? Which T/C sensor is for 4WD? I think thats the first one I need to tackle.

 

Honestly, it bothers me that it doesn't seem to be TRYING to get out of 4wd. No flashing light, no noise from the actuator, right? I would double check that button circuit by making sure you have ground at the pink wire at Pin 4 of the 4wd ECU when the button is pushed and also that the 4wd fuse by driver's knee is good. (The lights are powered by the GAUGE fuse so that doesn't mean anything.)

Thing is, bad switches usually result in flashing lights as the system starts the cycle, but can't complete it, or thinks it didn't when it did. I can't remember one like yours where they just stay solid. It's too bad the only way to test a 4wd ECU is test swap another one.

Anyway, as to which is 4wd all I know is it has a gray plug. I have a 5-speed J-shift so mine is different. To get to mine, I had to unbolt the transmission brace while I had a jack on it, and then let it sag a little. Some people can get to them through the shifter hole without that, but not me.

 

Yes it is.

 

Yea, I thought the same thing. I guess I have to at least try, I'll set the damm thing on fire before i give some dealer 4K for installing a new TC. I did do the continuity/resistance check as recommended by that service bulletin prior to jumping pins 2&3 and it failed, which made me think I'm done here but when the actuator moved multiple times with current applied to the right pins I got a lil hopefull. You'd think the Japanese would have given us some direction here, it's not like they don't know of the issue. I've been to Japan, if there's one thing about them they pay attention to detail. Any suggestions on a sequence of sensors to clean/check?

 

So how do I check for ground on that pin on the ECU assuming I can find it...I have to remove the harness to check, while actuating the switch?