99 Tacoma won't engage 4x4

Hey guys and gals,
I've got a 99 Tacoma and for some reason my 4 wheel drive won't engage. It's a 5 speed with manual 4 wheel drive lever. No push buttons. When I shift into 4 wheel drive I get no light on the dash and no power to the front tires. I can tell the transfer case is working cause when shifted into 4 low its apparent its in low range. Everything is factory except the small Toytec lift. No manual locking hubs. I've checked all vacuum lines and they appear to be hooked up. I've searched for posts regarding this issue and have come up empty. Any help to point me in the right direction is appreciated. Thank you.

 

Try to put it in 4 LOW. If it goes in and the light is out, the bulb is burned out. You will be able to tell if it's in 4 low.
Let me know what happens.

 

It goes into 4 low and all the low range gears work but no power to the front tires

 

Your front diff is still controlled by an electronic actuator at the front diff. It engages when you put it in 4wd as opposed to when you hit a button. So being electronically controlled. you do have the issue of stuff like bad grounds or fuses being the culprit. Look for it first then let us know.

 

Is it common for that actuator to go bad??

 

check your 4x4 module as well, its inside the kick panel on the drivers side. Also check your front driveline (maybe broken joint?)

 

Check your add switch on the top of the t case. If that goes bad it won't work

 

What's the 4x4 module look like? How to I tell if the add switch is bad??

 

You could supply 12v to the actuator and see if the 4wd then works

 

I'm having the same issue with mine also I have vacuum to the actuator tho an it's shifting in 4wd to trying to narrow it all down.

 

can anyone tell me how and where to identify the electronic actuator at the front differential? My front wheels are not engaging and the 4x4 light is not showing on the dash when I try to engage 4x4. Got stuck yesterday and could not engage the front wheels. Any other possible check suggestions would be appreciated.

 

There's a tube on the right side of the front differential. It's called an intermediate shaft or jack shaft. The ADD (auto differential disconnect) actuator is on the back of it.

 

Ok I put truck on jack stands with all four wheels off the ground. When I engaged 4x4 shifter the front shaft was turning but the front wheels weren't engaging. This told me to abandon checking the switches on the transfer case and so I pulled off the ADD indicator switch on the front differential and cleaned it well and tested the continuity with my multimeter, it was ok. Decided to check the vacuum on the ADD before I pulled it and had to drain the front differential since I couldn't find my 10 mm hex wrench to remove the drain plug and fill plug. So I followed the vacuum lines from the ADD to two switches mounted on the driver sidewall near the battery and fuse box. I borrowed a vacuum tester from Autozone and removed the vacuum lines from the switches and pulled a vacuum on the lines to the ADD. Then started the truck and engaged the 4x4 with the truck suspended off all four wheels. Whammo, front wheels engaged! So I removed, cleaned and checked the switch. It would definitely click when I bench tested with some alligator clips connected to a battery. One of the vacuum lines would hold a vacuum to it (the one to the ADD). So I cleaned the terminals good with some electronic cleaner and blew it out with my air hose to dry out the cleaner and blow out any debris. Reattached the plug and vacuum lines and 4x4 engaged perfectly but the dash light did not show 4x4 engaged. Then I remembered unplugging one of the transfer indicator switches on the transfer case in order to remove and check. (I couldn't get a wrench to it so I decided to go a different route). Plugged it back in and 4x4 indicator light came back on.

 

Wanted to thank you all for posting. I used your notes to help me figure out why my 4wd wasn't working after replacing my head gaskets (lost a water jacket @250k). I traced it down to a hose connection at the switches by the battery.