2008 Taco 4wd Issue

When I try switching into 4wd...nothing happens. The fuse is good. I tried the computer trick ctrl-alt-del by pulling the fuse for thirty seconds, reinserting and after 50 miles the 4wd works again. Any clues. I can turn a wrench and am confortable with a multimeter. Any suggestions would be greatly appreciated.

 

When you say it doesn't work you get no lights at all or it just stays flashing?


https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

Do you use 4X4 regularly?

The owner's manual "suggests" about 10 miles/month in 4X4. Personally, I think that is a little overkill, but I do make sure mine is in 4X4 for at least a mile or 2 anytime I find myself on a dirt or gravel road. It doesn't happen every single month and it is rarely 10 miles. But I don't let it sit unused for months at a time. And I may get in 200+ miles in 4X4 during some months. The key is that if you don't use it, you lose it.

Sitting unused for months at a time prevents internal parts from being lubricated. Grease in the hubs gets hard and they won't engage. Electrical components can corrode and fail to work from non-use.

If that is the case, just getting it out and giving it a good long workout in 4X4 may help and won't hurt as long as you don't do it on pavement or other dry hard surface. I've seen times where the hubs had to be taken apart, the hardened grease cleaned off and re-lubed. They worked fine after that.

 

4wd indicator flashes once when i start the engine. When I turn the selector switch, there is nothing. 99% of my time is spent on pavement. Drive 6 miles of dirt road once a month. The truck is sixteen years old and has 77,000 miles. I'm thinking bad connection or corroded wire somewhere. Seems like the actuator is the most exposed place to start testing for signal strength.

Any past experience is welcome.

 

If you get no lights at all we need to check power and ground to the 4wd ECU and the 2 inputs from the 4wd switch.

Backprobe the connectors and do a few checks, see the thread I posted above for the location and pinout of the 4wd ECU.

Key on, one meter lead to a known good Ground, and backprobe the wires below with a needle or other suitable tool.

Connector F12 Pin 5 (Violet) is power (should be battery voltage)
F12 Pin 6 (White/Black) is Ground (should be less than 150mV (0.15v))

If those check good then check the voltages on the last 2 items (2-4 & LO) listed in the chart in the thread I posted above and compare them to the expected values.

 

^^^THIS^^^
I have a couple of places near me that provide straight-line travel for 5-6 miles. I engage 4H on these roads when I'm on them, especially any time it's raining or snowing. When it isn't, I just exercise the actuators on the front diff/transfer case by engaging 4H and 4L back and forth a few times while sitting at idle in my driveway. It's those actuators (motors) you want to keep limber.

 

Thanks for all the great advice...I'll post my findings.