jtriv

I live in Northern Virginia and because of the recent snow I've been driving my 4runner into work in the snow. Up until the last 2 snows I haven't had any problems but in the last month when I press the button to shift to 4wd H, it does nothing, no light and it's definitely not in 4wd. I thought maybe something was freezing up because of the cold, but when I tried today in advance of the impending snow, I had the same problem. After driving around the block it began shifting in and out of 4wd and then finally stayed there. I just parked it like that. Was wondering if anyone had any ideas or suggestions as to why this is happening. Thanks

xcfunrunner

I had a similar problem. The sensor on top of transfer case wasn't registering that I put it into 4x4. For me, it works now without any fiddling. However, for about 2 months in the cold, I couldn't get it into 4x4 in my 96 4Runner. I have a 5-Speed though so I think the transfer case set up is a little different. I don't have any buttons on my lever.

TheDurk

Sounds to me like you are losing vacuum. Examine the hoses to VSV on the driver fender wall and the reservoir inside the fender with an unlit propane torch. Or test the system with a vacuum pump and gauge.

Giveaway is if you lose 4wd when you take your foot off the gas (weak vacuum in the manifold.)

flyinbrick

It is helpful to understand the system. Under the hood by drivers wheel well are two vacuum switches. One, when powered, applies vacuum to the actuator to unlock the transfer case to axle (2wd), the other locks (4wd). IIRC the brown back unlocks, blue front locks. Power is sent from the ecu. On my 5-speed, the shifter activates a switch on the transfer case telling the ecu to switch to send power to the blue switch and cut power to the brown switch. In the auto, I think the button does this. Anyway, start by confirming you have vacuum with a gauge at the vacuum canister (LF) wheel well and at the vacujm switches and have 12v at the appropriate vacuum switch. If the problem is not there, the next place to check is upstream at the transfer case switch or downstream at the actuator at the diff dependkng on what you find. In my case, it was the transfer case switch. I found the plug though the shifter opening, shorted it, and it worked. Eventually had a mechanic replace it since it required lowering the transfer case for access. Feel free to PM me if you need more help.