99 toyota 4runner transfer case problem

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01-23-2021, 01:31 PM

#21

Brandon J. Everett

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Quote:

Originally Posted by TheDurk

By pressure, you mean vacuum? You don't actually check the tube, you check the nipple the tube connects to. When you say 'line for the check' do you mean before or after the check valve? You need vacuum after the check so it reaches the two lines to the VSV's. If it doesn't, check may be installed backwards. You wouldn't be the first.

Did you check the 4wd fuse in the panel by driver's knee? (First suspect if no vacuum on both VSV's.) Check with a meter or swap with a known good fuse--DON'T tell me it 'looks good'.

If fuse is good, next step is to use a test light or meter to check if a 12V+ signal is going to the plugs on the VSV's. Check all four pins (two on each plug) in 2wd and 4wd. Also check in 4L.

Also confirm that front propeller shaft locks up when J-shift is in 4wd--I gather you have the J-shift. It should turn free by hand in 2wd.

You have the same setup I do--this should be easy. That multi-mode 4wd computer is a bear.

Ok Im coming in late to the party...I have the same issue as many here do... I have a 1999 taco, 3.4L, AT, with the ADD 4WD deal.
I have done a bunch of diagnosis based on the comments above....
I have vacuum and if I switch the lines the actuator will engage the front diff...
I have tested the plugs. the Orange side is always lit no matter J lever position. blue will not lite in any J lever pos.
Transfer case engages, and works in 4H/4L.

Where should i go from here.... TC switch? if so any help in finding it...do i have to drop the case? Could it be the relay or the module?

Thanks for the help!

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01-24-2021, 06:19 AM

#22

fierohink

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Quote:

Originally Posted by Brandon J. Everett

Where should i go from here.... TC switch? if so any help in finding it...do i have to drop the case? Could it be the relay or the module?

Thanks for the help!

almost all 4R problems source back to the position switches being faulty. When the positions don’t match the gear selector the 4wd module won’t allow shifting to occur.

The front diff sensor is on the backside of the diff around where the vacuum lines come in. It’s about the size of a spark plug with a simple 2 wire plug going to it.

next there are 2 sensors on the drivers side of the transfer case near the actuator. The final 2 are up high and usually require dropping the crossmember to get more room for your hands.

when you test the sensors for continuity with a multimeter, it isn’t just does it go from open to close. You have to test along the entire throw of the plunger to make sure there aren’t any dead spots. A lot of times you can spray contact cleaner into the tube around the ball and work them around and get dead spots to clean up. Sometimes you just have to replace them and they are around $25 depending on where you get them. (There are people that use off label sensors from reverse lights)

As TheDurk said, you also have to verify that your transfer case is shifting and locking up the front drive shaft. You can also apply vacuum to each nipple on the front diff and make your the shift fork inside is sliding.

if all your position sensors are functioning, and you transfer case and diff are functioning, next is the actuator contact traces. This is corrosion that builds up and prevents module from receiving info from the 4wd module.