flightjunkie
New member
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.
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.
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