4 wheel drive not working

So, I recently changed the fluids, including the crank case. But now my 4 wheel drive does not work. Could I have possibly done something that caused this issue? I've checked out a number of YouTube videos and found that is could as simple as the hose not being connected to as complicated as the actuator being bad. Fortunately, it looks easy to take apart. This is a 6-cylindor manual transmission.
Anyhow, tell me what some of your experiences have been with this and what I should be looking at. Thanks in advance!

 

Changing the fluid wouldn’t cause the problem.

If you want to know what’s wrong and not throw parts at it.
You’ll need a volt meter.
Take a look at the link below. Post your voltage result in the the link.
We will be happy to help you once we got your results.

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

 

Thank you for this! However, are we talking about a 2nd generation Tacoma? The color scheme doesn't coincide. Like I don't see a blue/yellow wire or red/blue wire. Then the voltages I'm getting are nowhere near what the chart says I should be getting on the wires that I can read.

 

Yes, this is for the 2nd Gen trucks.
Are you sure you are looking at the 4WD ECU?
You have to remove 1 bolt and take the panel down.

 

When you say it doesn’t work, does it do anything?

when you put it in 4hi, does the 4hi light come on and stay flashing? Or not at all?

 

Yes Tn, I did remove the panel and the wires look similar. Just not seeing some of the colors.

Yes Frank, the light flashes on 4H and flashes and beeps on 4L. When I was doing some of the back probing that Tn said to start with (when turning the key, but not starting the engine), I did notice that when I turned the knob to 4H I could hear what sounded like gears turning. But not going into 4 wheel drive. Anyhow, what should I check next?

 

I’ve seen ADDs get stuck a lot.

if you know where yours is, when you start up the truck, put it in 4hi, get out and lightly tap on the ADD with a hammer. If it shifts into 4hi (light goes solid), you know where your problem is.

 

What year model is your truck?
AFAIK, the wiring didn’t change colors, but I can see if the schematics are different for your year.

 

It's 2015

 

Thanks Frank. I'll give this a try. Hopefully it'll be as simple as that.

 

The 2015 diagrams show the same colors.
I’m not sure why yours would be different.

 

Thank you again everybody for your tips. Well, don't ask me what I did, but I HAVE 4 WHEEL DRIVE! All I did was check the fluid on the transfer case, check all the connections and hose on it to make sure they were secure. Then I did some back probing on the wires. Although I did pull the wire harness out to see the colors better then just snapped it back in. So somehow in all that, I got my 4 wheel drive back! However, the 4L still does not work. So while not fully fixed, at least I have 4H if needed. From what I've heard, it's not very often 4L is needed.
So the next question would be, is it worth the effort to fix the 4L? Could this lead to the 4H failing again at some point?

 

For me, yes. It’s worth fixing 4Lo.
I helps with hill descents. Keeps me from pressing the brakes too hard and kicking on the ABS.

 

I think it is worth the effort to try and figure out why 4Lo isn't working. Once you know why it isn't working, then you can decide if you want to fix it. You may choose to leave it non-functional, but there is some value in understanding why it doesn't work.

 

My 4wd went out over a year ago. Put the truck in 4Hi, it flashes for a little longer than usual, then light goes solid. Put truck in 1st gear, drove forward, and barely moved a foot even when giving it a bunch of throttle. Put the truck in reverse, and didn’t move an inch. Any idea what might be the problem?

 

You are saying the truck won’t move at all in 4Hi?

If so, something in the front differential is probably locked up.
I suppose it could be a badly seized u-joint, but unlikely.

 

No movement at all in reverse, and only the slightest movement in 1st gear but I have to be slipping the clutch out like crazy with a bunch of throttle to get some movement. Back story; driveshaft went out, had to send it out to get fixed, only option was to drive in 4Hi off the front axle for about a month. After driveshaft was installed, I never used my 4wd for about 8 months. Decided to go off-road one day, put the truck in 4wd, and that’s when I noticed the problem.

 

Hey Tn, one more question; while my 4 wheel drive does work (but still no 4L), what I'm finding is that it's now taking longer to engage. Meaning the truck has to go like a 100 ft before it kicks on. Could that be an indicator that it may totally go out at some point?

 

Most hateful device known to man kind, mine will eventfully work, often I have to switch it off and on a few times to get 4 low Many times I have had to turn the truck off and try again. Give me my lockout hubs and a floor shift back that worked every time! I'm in Maine we have to push snow, push in my case is the proper world hurling snow is not, that's why I need low range.

 

It’s not uncommon for to have to roll forward or backward a bit to get the 4WD to engage. If mine doesn’t engage with in a couple feet, I go backwards.

Actually, if it doesn’t engage instantly, I sift back and forth between Drive and Reverse. There’s usually just enough slack in the drive line to get it to lock in.

But there are times it takes mine a few feet to engage


Try going backwards and forwards next time.