4 wheel drive problem (4wd)
- Thread starter 99yota4
- Start date
MDTrailrider
New member
99yota4,
Have you solved the 4x4 problem?
I agree 100% with The Durk. Your problem is not with the light it is with the signal to tell the VSV to switch. The light will likely work if you solve that. By reversing the vacuum lines you have forced the VSV to keep the ADD in the 4x4 position so you've lost the benefit of the ADD.
I can't find the information I said I would look for regarding the three things that have to occur for the 4x4 light to illuminate. Your problem is one of those three. One of them is that the ADD needs to move to the 4x4 position. That's happening when you switch the vacuum lines so that's not the problem. I'm pretty sure another event is that you need continuity with a 4x4 switch at the J lever on the center console. I believe you also get that too since you appear to get 4x4 when you select it now that the ADD is forced to the 4x4 position.
I'm pretty sure you have a relay problem as The Durk suggests. The signal from the J Lever switch is not getting to the VSVs to change states. To test the theory, put the vacuum lines back where they belong and see if you can still get 4x4. I suspect you won’t.
I'll see if I can figure out where the relay is. I suspect you just need to find it, disconnect it, clean the contacts and maybe put some conditioner on them and reconnect the wires. In the worst case you probably need to replace the relay from a vehicle at the salvage yard.
The Durk,
Any chance you’ll be in EC anytime soon? I would still like to hook up with you at the Judge’s Bench when you’re in town.
Have you solved the 4x4 problem?
I agree 100% with The Durk. Your problem is not with the light it is with the signal to tell the VSV to switch. The light will likely work if you solve that. By reversing the vacuum lines you have forced the VSV to keep the ADD in the 4x4 position so you've lost the benefit of the ADD.
I can't find the information I said I would look for regarding the three things that have to occur for the 4x4 light to illuminate. Your problem is one of those three. One of them is that the ADD needs to move to the 4x4 position. That's happening when you switch the vacuum lines so that's not the problem. I'm pretty sure another event is that you need continuity with a 4x4 switch at the J lever on the center console. I believe you also get that too since you appear to get 4x4 when you select it now that the ADD is forced to the 4x4 position.
I'm pretty sure you have a relay problem as The Durk suggests. The signal from the J Lever switch is not getting to the VSVs to change states. To test the theory, put the vacuum lines back where they belong and see if you can still get 4x4. I suspect you won’t.
I'll see if I can figure out where the relay is. I suspect you just need to find it, disconnect it, clean the contacts and maybe put some conditioner on them and reconnect the wires. In the worst case you probably need to replace the relay from a vehicle at the salvage yard.
The Durk,
Any chance you’ll be in EC anytime soon? I would still like to hook up with you at the Judge’s Bench when you’re in town.
99yota4
New member
Hey MDTrailrider, thanks for the response. I have found the relay but I haven't looked at it yet. I found it using this thread as a guide http://www.toyota-4runner.org/3rd-gen-t4rs/44502-99-d-d-relay-location.html
If I check this and it doesn't solve the problem I will go to the local junk yard and pick up a relay, i know one that has several 4runner's and t-100s with the same motor and transmission. If those don't work out, what else could it be? switches on the transfer case? There are 2 switches to the side of the transfer case that I believe just unscrew and it's a push to engage, pull to disengage type of switch. I believe there was a test for that in the FSM that I could perform to check the functionality of that.
If I check this and it doesn't solve the problem I will go to the local junk yard and pick up a relay, i know one that has several 4runner's and t-100s with the same motor and transmission. If those don't work out, what else could it be? switches on the transfer case? There are 2 switches to the side of the transfer case that I believe just unscrew and it's a push to engage, pull to disengage type of switch. I believe there was a test for that in the FSM that I could perform to check the functionality of that.
MDTrailrider
New member
99yota4,
You posted while I was composing the following reply. I’ll post it for anyone else who has the same problem.
Inspect the relay as described in the FSM on page SA-50 found here. http://www.ncttora.com/FSM/1996/SIL...ypdf/02rmsour/2002/024runne/sa/acsy1/insp.pdf It is the second page.
The FSM shows the location of the A.D.D. Relay here. http://www.ncttora.com/FSM/1996/SIL...ypdf/02rmsour/2002/024runne/sa/acsy1/loca.pdf I can’t tell from the image if it is under the passenger side dash or in the engine compartment.
I thought I read the three events that have to occur for the 4x4 light to go on in the FSM but I can’t find it. I now believe I may have read it on a website when I did a search for “Automatic Disconnecting Differential”.
This information from a page I bookmarked last winter might be helpful to you.
>> When the transfer case gear shift is shifted into 4WD, the ADD system is actuated by the operation of the ADD solenoids located under the hood on the passenger side wheelwell. The solenoids are supplied voltage from the ADD relay which depending on the type of transmission the vehicle is equipped with, has it's ground completed by both a Transfer Position Switch and a Transfer Pressure Switch (V6 with automatic transmissions), or a Transfer Indicator Switch (4cyl.-- manual trans.). These solenoids control the vacuum signals to the ADD actuator which is mounted on the front axle. This actuator engages a sleeve inside the differential via an "intermediate shaft" which is attached to the driver's-side side gear shaft and clutch mechanism.
If the ADD system does not properly engage the front drive mechanism, the first items to check are the vacuum supply hoses. First, look under the hood and locate the ADD solenoids. Ensure that the vacuum hoses are connected to the solenoids or vacuum switching valves (VSV) as they are commonly called by Toyota. Next, look at the hoses at both the differential and vacuum reservoir located in the R/F wheelwell. Make sure all hoses are connected and not torn, cracked, or otherwise in poor condition. Once the system is engaged or disengaged from 4WD, it will stay in that position. Basically, if the system is not functioning, the vehicle can be placed in either 2 or 4 wheel drive manually with a vacuum source for testing. If you plan to leave the ADD system disconnected you will need to apply vacume from the engine to make sure the front end does not unlock.
The ADD relay can be inspected for operation as well. This relay is located under the instrument panel on the passenger side of the steering column. Check for continuity between terminals 2 & 6 and 1 & 3 (see diagram). Upon applying 12 volts continuity between terminals 1 & 4. Replace the ADD relay if it fails the above tests. The VSVs or ADD solenoids can be inspected as well.This is another resistance check so a DVOM is needed here as well. Disconnect the electrical connector from the VSV and check to see if the resistance is between 38-45ohms.<<
I found it at http://www.off-road.com/trucks-4x4/tech/the-automatic-disconnecting-differential-system-19259.htmlI
You posted while I was composing the following reply. I’ll post it for anyone else who has the same problem.
Inspect the relay as described in the FSM on page SA-50 found here. http://www.ncttora.com/FSM/1996/SIL...ypdf/02rmsour/2002/024runne/sa/acsy1/insp.pdf It is the second page.
The FSM shows the location of the A.D.D. Relay here. http://www.ncttora.com/FSM/1996/SIL...ypdf/02rmsour/2002/024runne/sa/acsy1/loca.pdf I can’t tell from the image if it is under the passenger side dash or in the engine compartment.
I thought I read the three events that have to occur for the 4x4 light to go on in the FSM but I can’t find it. I now believe I may have read it on a website when I did a search for “Automatic Disconnecting Differential”.
This information from a page I bookmarked last winter might be helpful to you.
>> When the transfer case gear shift is shifted into 4WD, the ADD system is actuated by the operation of the ADD solenoids located under the hood on the passenger side wheelwell. The solenoids are supplied voltage from the ADD relay which depending on the type of transmission the vehicle is equipped with, has it's ground completed by both a Transfer Position Switch and a Transfer Pressure Switch (V6 with automatic transmissions), or a Transfer Indicator Switch (4cyl.-- manual trans.). These solenoids control the vacuum signals to the ADD actuator which is mounted on the front axle. This actuator engages a sleeve inside the differential via an "intermediate shaft" which is attached to the driver's-side side gear shaft and clutch mechanism.
If the ADD system does not properly engage the front drive mechanism, the first items to check are the vacuum supply hoses. First, look under the hood and locate the ADD solenoids. Ensure that the vacuum hoses are connected to the solenoids or vacuum switching valves (VSV) as they are commonly called by Toyota. Next, look at the hoses at both the differential and vacuum reservoir located in the R/F wheelwell. Make sure all hoses are connected and not torn, cracked, or otherwise in poor condition. Once the system is engaged or disengaged from 4WD, it will stay in that position. Basically, if the system is not functioning, the vehicle can be placed in either 2 or 4 wheel drive manually with a vacuum source for testing. If you plan to leave the ADD system disconnected you will need to apply vacume from the engine to make sure the front end does not unlock.
The ADD relay can be inspected for operation as well. This relay is located under the instrument panel on the passenger side of the steering column. Check for continuity between terminals 2 & 6 and 1 & 3 (see diagram). Upon applying 12 volts continuity between terminals 1 & 4. Replace the ADD relay if it fails the above tests. The VSVs or ADD solenoids can be inspected as well.This is another resistance check so a DVOM is needed here as well. Disconnect the electrical connector from the VSV and check to see if the resistance is between 38-45ohms.<<
I found it at http://www.off-road.com/trucks-4x4/tech/the-automatic-disconnecting-differential-system-19259.htmlI
MDTrailrider
New member
I was just about to ask you where it was located. That’s very good to know but I hope I never need to check it.
Possibly but I don’t know how they work. It seems to me it’s unlikely because they would both need to be bad. If only one was bad the light would come on in 4L or 4H which ever one has the good switch.
I think the problem is with the ADD Relay. It’s not conveying the signal to the VSVs for some reason. The FSM does say to check the fuse first, the wiring harness second and the Vehicle Speed Sensor third. It doesn’t say anything about the ADD Relay in the troubleshooting table at: http://www.ncttora.com/FSM/1996/SIL...f/02rmsour/2002/024runne/trvf3am/trou/pst.pdf
99yota4
New member
It says in your last post that the ADD relay is located on the passenger side of the steering column under the instrument panel...I wonder if that is accurate and correct information compared to what I believe is the ADD relay on the passenger kickpanel as I posted earlier...
It also mentions that there are two switches that provide ground to the relay which are the transfer position switch and the transfer pressure switch. I wonder if those are the same as the 4wd indicator switches on the transfer case...
It also mentions that there are two switches that provide ground to the relay which are the transfer position switch and the transfer pressure switch. I wonder if those are the same as the 4wd indicator switches on the transfer case...
MDTrailrider
New member
The relay in Charlesc76 image doesn’t look like the diagram on page FSM page SA-50. The diagram shows a connector with 10 positions and 9 of them occupied. His image shows only 6 positions. The series of tests include 8 wires, all but 5 and 8, and 8 is shown as a vacant position on the diagram. His connector only has 6 positions so either his truck is different or we’re looking at the wrong diagram. I would do what Charles did if I were you. I would look at the FSM wiring diagram to establish the colors of the nine conductors and find a relay with a matching wiring pattern. I would look in all three places until I found it. That’s the best I can suggest.
I don’t know. I don’t know what the transfer pressure switch is. The author of that information may be describing a different model year that doesn’t work quite the same.
TheDurk
Elite Member
Hey, Trailrider. I sent you a PM.
99yota4
New member
I am more convinced that it may be the relay or switch on the front diff. I had my brother drive it in 2Hi and I saw that the front propeller shaft is not rotating. The CV's are but that's the way it should be because they are "constant velocity" right? When I say propeller shaft I'm talking about the on that runs from front to back from the transmission. Anyway, When shifted into 4Hi I see that the front propeller shaft is rotating. So the switches there should be fine. I am now led to suspect the relay or front diff switch. The relay that was in the passenger side kickpanel said "transmission relay" Which I'm not sure if that is the ADD relay or not. The FSM diagram make it appear as if it in the passenger kick panel though... i'm confused
Diagram14
New member
You have the exact situation that I have now with the TC sending power through the front drive/propeller shaft to an unengaging front diff. in 4Hi and more than likely 4Lo. I got my hands on a cheap multi-meter and hope to pull the front diff. switch and run continuity on it in the next couple of days. If youre considering doing the same and beat me to it let me know what you find.
99yota4
New member
Yea I won't be able to do it for a while since school is back in session in full force. I would check the relay first and then do the switches. The relay is probably easier to get to if we can find it. According to some info on the web, it's located on the passenger side of the steering column behind the instrument panel. But the illustration on the FSM makes it appear on the passenger side kick panel.
TheDurk
Elite Member
You still don't understand what the switches on the TC do, I'm afraid. They don't MAKE the shaft engage. They TELL the front diff and the 4wd light that it DID engage. The engagement is done directly from the handle. The switches are activated by a push button in contact with the gearing and open or close depending on whether the 4wd is actually engaged. Same with the switch on the front diff. It REPORTS, it doesn't cause. The switches on the TC only CAUSE the FRONT diff to engage, whenever the TC is in 4H or 4l because they make the vacuum to switch from one hose to the other. The light goes on when BOTH the TC and the front are in 4wd position, according to the switches on each. You have no reason to suspect the switch on the front diff because it could NOT cause the problem, it only helps turn on the light.
Since there are separate switches on the TC for 4H and 4L, the relay is the logical culprit since you have problems on both and one bad relay is more likely than 2 bad switches. Of course, the issue could be a short or open in the wiring, too.
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99yota4
New member
Thank Durk. I'll have to get in there and find the relay. When I take the relay out, How do I test it? If that's not the problem, I will need to remove the two switched on the transfer cases but it is difficult to get any sort of tool in there to loosen it. Any tips on how to remove the switches? If both of those check out then I'm led to suspect that the wiring somewhere along the way is cut and not sending the signal to the relay. Correct?
TheDurk
Elite Member
The test procedure is in my FSM. Basically, you check continuity between various terminals and then you energize the coil and check again. If you can't find it elsewhere on-line, I'll walk you through it. I don't have a scanner anymore, it doesn't do Windows 7 and needs a parallel port that I don't have any more either.
I have not had to mess with the transfer case switches so I can't help you there.
99yota4
New member
I just got off the phone with a part/tech at Toyota and I asked them to tell me where the A.D.D. Relay is for my particular 4runner. They told me that THERE IS NONE?! "Chuck" claims that based on their technical info site, the 4wd system is controlled by the 4wd ECU located on the drive side kickpanel. Can anybody verify that this is true? I am going to take the 4runner to a shop where the guy is pretty knowledgable with toyota's. They are going to take a look at my exhaust system (P0420) and hopefully this 4wd issue as well...
Also anyone know where to access the 1999 FSM? The ttora site has a 02 and that is a totally different system than a 99. Thanks
Also anyone know where to access the 1999 FSM? The ttora site has a 02 and that is a totally different system than a 99. Thanks
99yota4
New member
PROBLEM IS FIXED!
well there really wasn't much fixing to do. I talked to a few local shops and they all suspected the switch on the passenger side of the transfer case that wasn't connected to anything was very suspicious. When I looked at the FSM, it looked like it said that switch was for the center diff lock, which I don't have. I assumed it was one of the "dead end" wires that toyota is known for. I took it into toyota today to ask them what exactly that switch was for and the tech said i bet there is a wire on top of the tranny that is not plugged. Sure enough, he found a lead and fished it over and connected it, and what do you know? 4wd light works and everything is good again! I should have done a more thorough search for loose wires around the transmission and transfer case. At least I got to learn ALOT about my 4wd system. Thanks goes out to TheDurk, MDTrailRider, and everyone else who chimed in!
One last question remains, What is the proper way to engage 4LO? 4Hi is on the fly so I can do that as long as my speeds are low. However, whenever I'm at a full stop and try to shift into 4LO from 4HI, it grinds, and its worse when I want to shift back into 4HI. I've tried it in Neutral as well...What is the proper procedure?!
well there really wasn't much fixing to do. I talked to a few local shops and they all suspected the switch on the passenger side of the transfer case that wasn't connected to anything was very suspicious. When I looked at the FSM, it looked like it said that switch was for the center diff lock, which I don't have. I assumed it was one of the "dead end" wires that toyota is known for. I took it into toyota today to ask them what exactly that switch was for and the tech said i bet there is a wire on top of the tranny that is not plugged. Sure enough, he found a lead and fished it over and connected it, and what do you know? 4wd light works and everything is good again! I should have done a more thorough search for loose wires around the transmission and transfer case. At least I got to learn ALOT about my 4wd system. Thanks goes out to TheDurk, MDTrailRider, and everyone else who chimed in!
One last question remains, What is the proper way to engage 4LO? 4Hi is on the fly so I can do that as long as my speeds are low. However, whenever I'm at a full stop and try to shift into 4LO from 4HI, it grinds, and its worse when I want to shift back into 4HI. I've tried it in Neutral as well...What is the proper procedure?!
theizzardking
New member
here's a thread on that very question
http://www.toyota-4runner.org/3rd-gen-t4rs/31910-engage-into-lo4.html
99yota4
New member
word. Thanks theizzard, So it's
1. stop
2. shift into Neutral (transmission)
3. wait a few seconds
4. Shift into 4Lo from N (Transfer case)
What about disengaging? It grids MOST when trying to go from 4Lo to N then 4Hi. I would assume, stop, neutral, wait a few seconds then back into 4Hi?
1. stop
2. shift into Neutral (transmission)
3. wait a few seconds
4. Shift into 4Lo from N (Transfer case)
What about disengaging? It grids MOST when trying to go from 4Lo to N then 4Hi. I would assume, stop, neutral, wait a few seconds then back into 4Hi?
theizzardking
New member
thats what i do or sometimes i even just kill the engine, then shift lol, i feel your pain my butt puckers every time i hear those gears grind
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