4WD won’t engage

My 2007 4x4 suddenly just stopped working. When you switch to 4hi on the dash, the green light flashes, but never turns solid, & the 4x4 never engages. 1st I tried to get a reset by disconnecting the battery for 10 minutes and then re-connecting it. That changed nothing. Next, I checked the 20A 4wd fuse in the auxiliary fuse box. (Under driver side dash) It was still good. Pulling the fuse and starting the car causes all 4x4 lights on dash to come on and stay on solid. (I guess that tells you the fuse is blown). I previously tried all the standard hacks. Backing up, pulling forward, turning 4wd on ang off several times, driving fast & turning it on. Driving slow & turning it on. Sitting still, etc, etc. Next I went under the car & checked the center actuator. Aha! I found the vacuum hose detached. Easy fix, right? Dead wrong! Absolutely nothing changed when re-connected it. I checked the hose for suction with the engine running & the 4hi light flashing. NO suction. I checked the front actuator next. NO suction. Both hoses seem intact all the way to the steel tubing which disappears into the tranfer case on the center actuator, & up into the guts of the engine compartment on the front actuator. All wiring still looks good. Can remove the actuator covers without spilling a bunch of oil? It seems like there must be a bad valve or something upstream in the vacuum system for both actuators to fall at exactly the same time. If the tranfer case won’t engage, I can’t see any way for the front diff to engage either. Any ideas? HELP!

 

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

 

Those hoses are vent hoses. The system doesn’t operate on vacuum. It’s electrical.

 

Yes, that is just a vent hose. The problem is that you don't know how long or in what kind of weather you've been driving with that vent open.
They get a little water in them like when you're driving in the rain, and the contacts corrode. The traces aren't very thick and they wear through or simply stop making good contact.
You'll have to pull that cover and have a look. There are videos on YT showing how to do it.

 

You are going to need to see the link in post #2.
Since the hose was off, you likely already know where the issue is.

If you choose to remove the cover. Don't remove big white gear unless you have to.
And if you do, make sure you take note of how the contact fingers are pointed.
Other wise, you'll have to time the gear. Not a big deal. But it can be "tricky".

 

I read another post saying that you could manually turn that plastic gear to get the 4x4 to engage as a hack if you were in a pinch. I looked up the cost of a whole new actuator & it’s not pretty. The Toyota Parts OEM Website has the center actuator for $1400. There is also a $90 aftermarket one on another website. Anybody know if these aftermarket cheap parts will get the job done? I’m certainly not paying $1400.

 

I'd really reccomend following the tests outlined in the thread posted above and posting your results here so we can verify that's the problem before you start winging parts at it.

The cheapos on Amazon/ebay are hit or miss wheather or not they will A: work at all, B: last awhile.

 

I pulled the cover off the center actuator. I figured since the vent hose was detached, I would find some evidence of water inside. There was a lot of yellow grease all over the contacts and brushes. It seemed like it was just lube coming out of the main screw/ motor. Would that grease be flux? After cleaning it, the whole unit looks immaculate. No corrosion. No evidence of water. Still, after pulling all the plugs, running a blow dryer on everything to make sure there’s no water in the electrical, I re-assembled everything and got nowhere again. Next I’m going to run the tests DM93 is recommending. I also would like to have a look inside the cover of the front actuator too.

 

Do the test Dm93 has laid out in the link above.
No need to pull any more actuators apart.
The test will tell you where to look.

The grease is dielectric grease. It's there to help prevent corrosion. It works good for humidity.
But once water gets in there, that grease doesn't do anything.
That grease is also EXPENSIVE. Not that you'd actually buy it from Toyota, but you can......

 

Yea we discussed it some between page 23 and 27 of the 4wd thread.

 

I remembered reading it. Wasn’t sure where.

 

I guess when I get this problem solved, I should get some more dielectric grease and ad some more to the actuator. Just waiting for it to warm up outside so I can run this voltage test. Typically, my 4x4 only goes out when winter storms are menacing the Tahoe Area. It’s been snowing every day since the 4x4 went out. It was 9 deg. F this morning. That’s why I mentioned the “manual” hack of turning the actuator gear by hand. Anybody out there willing to confirm if that is a viable emergency fix? If the voltage test doesn’t provide a solution.

 

That would get the transfer case into 4wd but you would have to figure out how to get the ADD locked in, it's not nearly as easy to access.

 

Use it or lose it. All posts previous are your cure.

 

I did those tests about the 4x4 voltages. There are 4 not showing normal readings. I attached a photo of the expected & actual voltages.

 

Looks like a bad 4wd position switch on the back of the Transfer Case Actuator, we can verify this by unplugging it and jumping the terminals with a small paperclip then verifying 4WD (B22) goes to 0v.

 

Not sure what you meant by that Sorry. Testing in this way is something new to me. I’ve pulled parts and found out if their bad by testing resistance, but this is way better. Can that switch be obtained separately if it turns out to be bad?

 

Ok. Now I see where you are going with this. I have jumpers & a good multi-tester. I used sewing needles for the first test.

 

Yes one is the sense wire (Red/Blue) and the other is ground (White/Black), just jump across them and verify it goes to 0v at the 4wd ECU. That will verify our circuit integrity.

Also need to verify with the switch in 4wd that the front driveshaft is locked in.