1998 4Runner automatic 3.4 limited. My 4wheel drive will not engage when I push the button. At first it happened once in a while and you had to push the button a few times but now nothing. I took the switch on the 4wheel drive gearshift apart and there is no power going to it. Checked the fuses. Is there supposed to be power going to that switch? If not anyone have any ideas. I checked all the connections on the transfer case and all over and everything looks hooked up.

Thanks. Its snowing here and I need some 4wheel drive.

 

Have you tried putting it in Neutral before shifting into 4WD?

 

That switch goes to ground. If you find more than a volt or two something is wrong.

First thing to do is see if issue is in t-case or front diff. Can you hear the t-case actuator engage? Does the front shaft lock up in 4wd? Does the indicator not flash when you try to engage? Did you check the 4wd fuse specifically, using a meter or test light or known good fuse? (Do NOT tell me "it looked fine" or I will tie your nutsack to my winch line.)

 

I cannot hear the t-case actuator engage. The Front shaft does not lock up in 4wd. The indicator does not flash at all. I replaced the fuse with new ones out of the box. I ran a vacuum pump to both lines to the actuator and pressured them up. Neither engaged the 4wd.

 

I had to replace my vacuum lines on mine last year.
they had pin holes in them from age




goodluck

 

@TheDurk

What does this mean?

 

I dealt with something like this for about a month, following the "4wd won't disengage thread", which has a lot of good information about these systems. I eventually got to the point where I found an actuator connector pin was not contacting the female side properly in the connector and the actuator would not complete the movement to the desired setting. I found this by first wiggling the wire going into the actuator. When the problem occurred again, I thumped the connector and each time the actuator would complete the movement successfully. I took a paper clip and dinked with the female side of the connector a little bit and now it works every time. Just a thought and something to check without taking all the sensors out and everything apart like I did.

 

It looked fine from here!!

It comes down to figuring out is this electrical or mechanical.

Since I don`t have any hands on with this system I will stick with.

It looks fine!!

 

If I try and engage the 4wd going over 65 or 70mph the 4wd light comes on and beeps. That doesn't happen when its under that speed. That probably narrows it down a little. I ordered a new actuator sensor. $40. Thats not too expensive to try out. I ran a vacuum tester on the lines. They will hold 20lbs of pressure steady.

 

I guess you mean that they will hold 20 inches of mercury vacuum.

 

No, I don't know what that means. I don't know anything about the vacuum system. It's not lbs?

 

Vacuum is ordinarily measured in inches of mercury.

 

Got it thanks. Didn't know that. If you can't learn something new every day until you die you ain't paying attention.

 

Do I have this correct ??

Your trying to engage 4wd going 65mph and over !!

If you need to engage 4wd why are you going that fast??

Your systems works fine below 65 mph??

This is like questions I get at work I am running .045 wire at 24 volts but I keep burning through the 16 gauge metal.

I think the welder is broke.

 

No the system does not work fine below 65. There is something wrong with it. I'm trying to figure out what it is.

 

So I've narrowed this whole thing down a lot. The Vacuum system is working fine. When I apply vacuum pressure to the 4wd line by the VSV to the actuator 4wheel drive engages. When I apply vacuum to the other line 4wd disengages.

The 2wd side of the VSV has constant vacuum pressure. When I switch the hoses to the actuator the 4wd engages. However when you push the 4wd button the power does not switch over to the 4wd side of the VSV. I used a test light and the power stays on the 2wd side of the VSV and does not move to the 4wd side of the VSV.

I guess I could jumper power to the 4wd side of the VSW and see if it engages, but that would not terminate power to the 2wd side. I could unplug the 2wd side and supply power to the 4wd side. Maybe thats' not a good idea.

Anyway the problem is in between the 4wd switch and the VSV. So as I understand it, there is a 4wd control unit behind the drivers side kick plate, and I think there is a 4wd relay behind the passenger side air bag or somewhere up in there. I sure couldn't find that relay. Anyone know if it has a relay in there or is it all controlled by the 4wd control unit.

 

5-speed has relay on passenger side. Auto has 4wd ECU on driver side. Never both. Your fault could easil be a T/C sensor switch. Check those first, before messing with relay/ECU. You could MacGuyver a 2-way switch to the VSV's to control ADD from the cab, but it would be more work than doing it right. Last resort only.

 

Hey thanks. Is the the T/C sensor switch?]

I replaced it already.

 

Totally solid advice and I hope he is jesting about the winch line......I would not test this however!

 

Ok one more shot at this. I have verified the t-case selector switch is properly grounded on one side, and there is continuity on the other side to the 4wd computer unit shown in the picture. However still nothing when I push the T-Case selector switch. However, when I run 12v power into the wire that goes from the 4wd computer unit shown in the picture to the 4wd side of the VSV, 4wd engages. I'm thinking the problem is in that 4wd computer unit. Signal is going in, but not coming out. Any thoughts? Thanks.