seng

Hello!

I posted this on another forum and was advised that I may have better luck here. This is my first post. Thanks for looking it over.

I just purchased a 1994 4-runner, and I noticed that the 4 wheel drive wasn't working. I noticed that the ADD relay was unplugged. I plugged it back in and the 4 wheel drive works, but when I take it out of 4 wheel drive into normal drive, After going only a few feet, the 4 wheel drive tries to engage on it's own and it throws me into 4 wheel drive mode. To take it out of 4 wheel drive I have to unplug the ADD relay. Does anyone know what's wrong? I took it to a local dealer and tried to have the diagnostic run and after 6 hours thay hadn't solved the problem and wanted to go into a deeper diagnostic for more $$ and there were still no gurantees that they could figure out the problem so I just brought it home.

I changed out the actuator, the ADD relay and VSV valve and still had no luck - it has the same problem (parts I tried were from my other 4 runner a '93 and all parts worked fine in the other truck.)

If anyone can help I would appreciate it!!

Thanks! Seng

breknraj

Double check that your vacuum hoses are routed properly, and in good condition. Also, check that the vacuum cannister under the front passenger fender is in good shape.

eric-the-red

When you shift to 4wd the switch on the transfer case grounds the ADD relay, which then activates the 4wd vacuum valve. Check that switch, there should be no continuity between the terminals when in 2wd. Or you could have a shorted wire in that circuit which is grounding the relay.

seng

Thanks for all of the advice!

Does anyone know if it could be the transfer pressure switch? A Toyota mechanic told me to check the transfer pressure switch. I will check it, but it is going to be work getting to it since it is under the transmission and so I will have to take the transmission off to access it. What exactly does the transfer pressure switch do anyway?

Happy Thanksgiving!!

~Seng

seng

Thanks for the help

Which switch are you talking about? Are you talking about the transfer pressure switch?

seng

Thanks for the advice. I checked this and it this isn't the problem. The hoses are fine and routed properly.

eric-the-red

The switch I'm talking about is on the side of the transfer case on 5 speed vehicles. It detects when you move the shifter into 4wd and engages the ADD. If you've got an auto trany then they're more complicated as they have a hydraulically activated transfer case, and then you would have the pressure switch.

da_bigg_wigg

When my 4wd was on the fritz, it actually ended up being that switch. Perhaps your switch is stuck into the on position or something. It's easy to test though. Just see if there is continuity when you have it in 2wd. I somewhat doubt this is the problem. And no, you don't need to drop your transfer case. It's a pain in the ass, but you can get at it. To test it you don't even need to remove it. You can easily unplug the wires and test that way.

seng

I got it working!

I actually have an automatic transmission... I found out that it was the transfer pressure switch. the transfer pressure switch is in the transmission pan (the small pan, not the large pan). I just replaced it and it is now as good as new.

Thanks for all the help, I appreciate it!!

Seng

MadeInJapan91

Your 4runner is possessed.Take it to a Shinto priest for exorcism......

keirnan

i just figured out how to post.

Designsbyme

Sounds to me like it wants you to take it wheeling!

keirnan

i have a 95 SR5 5 speed, with same problem. wants to engage 4 wheel drive while moving. transmission people and dealer all said its the transfer case, a fork on the shifter "broke" off and needs replaceing/rebuilding. both estimated 8-9 hours just to see if thats the problem. unacceptable. can anyone help a novice find out what an ADD relay is or where to find it? HELP!!!!! arg. (lol)
i have a haynes manual but there is no mention of it. at first the dealer said to adjust the shifter on the transfer, but its the kind that goes down in the unit not on the side, that much i know. also know that i took off the front axle so it would stop grinding. hey, is there a way to dis-engange the 4 wheel drive all-together? i dont care if i have 4 wheel drive right now, i need to drive the truck and not worry its gonna catapult. what a mess, eh? any help would be greatly appreciated.