How To Trouble Shoot 4x4 Actuator

Given the mileage and the fact that these things seem to universally shit the bed I wouldn't be worried about OEM anything at this point. Just get a good gear grease of any kind, the only need is to lubricate the gears, it's not stopping water intrusion.

Edit: okay when I thought about it the breather tube might be useful since it utilizes a rubber o ring type gasket for the plastic electronic housing and the metal. I suppose if you went from low altitude to higher it could potentially break the seal allowing water intrusion if you drove in wet weather. Same for hot and cold air and the plastic and metal expanding and contracting at different rates. In other words saving a buck and making the electronic housing the same metal would have likely cured all this with no need for a breather tube and water intrusion for many. Just my guess. I don't have a water issue but now I suspect my ADD switch. I did inspect it but I should have used my multimeter on the damn thing

 

Okay my ADD detection switch fails to open when in 2WD. The actuators are working I can hear them but I'm positive it's that switch or wire or ground.

So, because I stupidly didn't take my multimeter to the damned switch can anyone tell me which pins it closes when 4WD is engaged? I can literally Unplug it and test the contacts to rule out whether that switch is open or not and not just a wiring issue to the ecu. I'm going to guess 4 and 6 because they were closed when I bench tested it. But I should have tested continuity at the switch itself.

 

At the ADD actuator connector:

ADD detection is pin 3 (Light Green/Black)
DL1 is pin 6 (Light Green)
DL2 is pin 5 (Pink/Blue)

ADD and DL2 should be 0v in 4wd and 12V in 2wd.
DL1 should be 12v in 4wd and 0v in 2wd.

More info on the 4wd system here:
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

I believe I found the issue. Help me track this I'm tired right now so I may be off.

At the wiring harness (disconnected from actuator) pins 3 and 4 are connected. So my ADD is connected to ground the entire time and it'll always read as open or 0V resulting in this failure. The pins for 5 and 6 give me no continuity and of course 12v when referenced to ground and battery on. Pin 3 is continuous with 4 ie ground and 0v as expected with vehicle on.

The computer will think the ADD switch is always closed if there's no signal sent to it, right?

The actuator itself, when probed, has no continuity between 3 and 4 unless it's in 4WD as expected. I'm assuming that's what the ADD sensor switch does is provide that path to ground when engaged. So I believe the switch is working, it was clean when I looked at it. It's just getting bad input.

Correct me if I'm way off base here. And if I'm hitting it close to home, what would be the cause? Floating or bad ground somewhere? A quick look at EE and ED seem okay. I could always brush those points up but I don't see anything obvious like corrosion or broken wires. I think the only other place for ground was EE but I gotta pop the whole air intake off to check that. While quick it isn't worth worrying about unless I'm on point and I'm not sure that I am. I got 5 other things I should be doing right now I'm just so pissed off lol

 

Can't really understand what kind of test you did.

The voltages I posted above are with the actuator plugged in and backprobing the wires at the connector, with the actuator unplugged you should see 12v on pins 3, 5, and 6. If any of them are 0v with the actuator unplugged you either have a broken wire or failed 4wd ECU.

 

Okay that's what I thought. For clarity sake and anyone following along let me detail what I did.


Here's what I tested: in 2WD, battery off, continuity (resistance test)
At the actuator, harness unplugged, testing harness pins. Pin 4 to ground, near zero and obviously continuous as it's the ground pin. Pin 3 (ADD switch) to ground. Continuous, slightly higher resistance. All other pins are not connected to ground. With battery on, Voltage test, I get nothing on pins 1 and 2 since actuator motor isn't running. 5 and 6 I get 12v to ground. 3 is 0v and 4 shows zero as well... which makes sense if it's grounded out. So on the wiring harness itself, 3 and 4 are connected in some pathway yet unknown.

Leaving unplugged at actuator, I unplug from ECU and test the other way on the harness. As you'd expect all the corresponding pins to the ADD aren't connected but 3 and 4 are. So that tells me somewhere in the wire harness itself, from actuator to ecu, the wire to sense the ADD switch is grounded out when it shouldn't be.

With battery on, I tested AT the ECU, NO harness attached: pins 12, 13, 23, 24, 25, 26. The ECU shows them all at 12V. Specifically Pin 26 for ADD switch so it is sending the right signal but it appears to be getting grounded somewhere in the wiring harness so it'll always show closed to the ECU no matter what state it's in.

Does any of the make sense?

So my next question is... and not one anyone can really answer: where is the break? :'(

 

Kinda hard for me to follow what you did but yes if I'm following correctly it sounds like the ADD Detection circuit is shorted to ground.
You could confirm this by unplugging the ADD and checking voltage on pin B26 at the 4wd ECU with both ECU plugs plugged in and the key on, if it's 0v with the ADD unplugged then it is shorted to ground somewhere between the 4wd ECU and the ADD.

 

It must be an intermittent short somewhere. Otherwise Id think the 4WD lamp would always blink and never complete the shift.

 

Hey guys, thanks for all the info... I was reading it and was really helpull. Nevertheless I think I have another issue in the ADD actuator. I have the same symptoms of flashing 4hi light and no 4lo connection, but taking off the actuator, it´s working fine. The issue is that this tiny lever marked in red (Does anyone knows the name?) isn´t working, it has no power... this gaves the signal that the front diff it is properly connected... so, my actuator is fine, but since the computer does not receive the signal that it is connected, it keeps the 4wd light blinking. Has anyone solve it?

 

time for a new one, chalk it up to being just another victim of cheap crappy design.

 

When you say the lever isn't working you mean it doesn't move or it doesn't make connection? I soldered mine when I had it all apart.

 

That is the ADD Detection switch, it should be open (12v) in 2wd and closed (0V) in 4wd. To my knowledge it isn't available separately from the actuator.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

New to the forum and I have been procrastinating getting my 4wd fixed. Mine engages but the 4hi light flashes, can’t go into 4lo and to go back to 2hi have to switch the selector back and turn the car on/off then I hear the click and am back into 2hi. I haven’t jacked up the truck, but assume since mine engages (immediately feel the difference while driving) the front actuator is not locking, so I only feel the 4wd cause the driverside wheel spins but not the passenger side, like many videos showing when the car is on jack stands.

I opened it today and this is what it looks like inside. Looks like the guy before me had sone the soldering job already and I am just assuming from the condition the motor is in, I am gonna need a new one.
I will post again once the new one has arrived and I have it installed.

 

Never had time to look into it, but Id bet that switch is an off-the-shelf part that can be had from the large electronics supply houses. The 3rd gen uses two of those in their T-case actuator plus all the ADDs.

@man_4x4 if you want you can very carefully pry the black plastic cap off the switch. Red arrows indicate where the black cap clips onto the grey body. The white lever with some super tiny metal contacts will fall out. From there you can try cleaning it all up and very lightly scuffing any oxidation off the metal contacts on the lever and in the body. May or may not work, but could potentially save you a bit of $

 

Well guys I am at a loss with this ADD. So two post above I posted a pic of my ADD when I took it out and ordered a new part. I had installed it back on waiting for the new one to get here and had topped off the diff oil. The oil that came out when I first took the ADD out was sludge. I bought this truck awhile back so not sure when the front diff oil was changed.
Anyways, the new ADD gets here today and where the electrical harness attaches is broken (it didnt eventually so its being returned). I head down to the truck just to see if it would stay on regardless. I turn the truck on and with the old ADD still on, I turn the dial to 4H and it slams right into it, 4Lo and no problem. I do this 3 times and every time it works great. Until the 4th time it jams up and just flashes.
When I take the old ADD out I notice the fork is in the middle, as if the gears inside the diff weren’t exactly lining up.
Anyone have had this issue? I am now gonna fill the diff with new oil (maybe that was the problem) and if not just gonna have to order a new one from the dealership I guess.

 

Are you sitting still when engaging 4WD?
I find that sometimes, you need to let the truck roll forward or backwards a little.

 

Up to this morning anytime I engaged the 4WD I have driven long distances with it and it has never clicked in. Just the light flashing. Today was the only time it went solid. I did think afterwards that on the 4th time maybe I should have gone back and forth a bit to see if it would click.
On that note when the ADD is taken off and I can move the sleeve from passenger side to driver side, I noticed that it jams up in the middle until I turn the front shaft while pressing on it before it clicks fully. So my question is do you guys know if the motor in the ADD continually pushes the sleeve until the gears line up or should these gears always line up and I might have a bigger problem?

 

Agreed, most of the time you will need to be rolling when switching the 4wd for everything to line up and engage.

 

Yes both the ADD and the Transfer Case Actuator have spring loaded "wait" mechanisms so that the motor can move to the proper position, then when everything lines up the spring will move the shift mechanism into place and trip the detection switch.

 

Thanks that’s really helpful to know! Imma fill up my diff (as my luck would have it I also stripped the drain plug, but most of the oil came out when I changed the ADD much more than the first time so that tells me initially it was running low on oil) and see what happens. Just wasting money on good old gear oil.