2009 TRD offroad won't go into 4WD

Hello, just accepted as a member and have a question. Not much use for 4WD down here in SC, but yesterday I had an occasion to need 4WD. When I turned the knob to 4H, the green picture and the yellow Lo symbol started flashing and wouldn't go away no matter what I did. Turned the knob back and forth, turned the ignition off and back on, still the same. When I got home I tried to get it to go into 4WD and I don't think it ever went in. I have used it many times when I lived in the Northeast so I know how it supposed to work. It also has ATRAC if that matters. Any ideas what's wrong??? I don't want to take it to the Toyota dealer...

 

You may want to check the vent hose on the Transfer case actuator, if it is cracked or disconnected likely water and dirt have gotten inside and corroded the contacts.
They can be taken apart and cleaned, sometimes this fixes them and sometimes not.
I have alot of information about the 4wd system compiled in the thread below.
https://www.tacomaworld.com/threads/4wd-system-operation-help-thread.742420/

 

Thank you for the information. Very thorough, sorry I didn't look hard enough at first.

 

No problem, yea the native search function isn't the greatest the google search works a little better.
If you have any other questions about it I'll do my best, I haven't had the opportunity to actually put my hands on a broken one yet but I've gone through the workings of mine the best I can to determine how it's supposed to work.
@6 gearT444E knows the inner workings of the actuators pretty well.

 

I can tell you to buy the Toyota OEM replacement mechanisms. Do NOT go cheap and buy 3rd party!

I went the cheap route and had to replace a 'new' 3rd party ADD actuator with a factory Toyota ADD actuator. PIA , the new 3rd party ADD actuator failed within a day or two after installing it.

You can find genuine Toyota actuators on Ebay almost at the same cost as a 3rd party from Rock Auto or Amazon.

Just trying to save you some time and energy.

 

When was the last time you used it in 4X4. They recommend about 10 miles/month in 4X4 in order to keep the internal parts lubricated and to ensure electrical connections don't corrode. Exactly 10 miles/month each and every month may not be necessary, but occasional use certainly is. If it has been 6 months or longer you may simply need to take the hubs apart, give everything a good cleaning and reassemble. The grease can harden from non-use and not allow the hubs to lock.

 

I agree the 4wd needs to be engaged regularly to help prevent problems but 2nd gens dont have disconnects at the hubs, the front axle is disconnected by the ADD Actuator on the front differential. Ford is the only maufacturer I know of that still uses locking hubs on their trucks, everyone else uses an axle disconnect exept some Dodges that don't have an axle disconnect at all.

 

It's good practice on 4wd Tacos to activate the system every once in a while preferably on soft ground to keep components like the ADD from seizing up. If you must do it on asphalt make you're going in a straight line and DO NOT MAKE ANY TURNS.

 

Thanks for all the great information. I checked all the electrical connections and they all appear to be OK as well as the vent tube being in place and in good shape. I also checked the ground from the engine to the firewall and it too looks good. I am going to dig in deeper on Sunday. One question, is there a ground near the transfer case, or does it rely on the engine ground??? I plan on probing the connector at the transfer case. According to the diagrams you guys provided, in 2H I should see 0volts on pin 5 and 12volts on pins 3 & 5 with the vehicle running. Can I do a resistance check on pin 5 with the vehicle off and the plug connected???

 

You’d be better off doing the check from the 4WD ECU behind the glove box.
You’ll have access to all the wires you need, and some of them even have different voltages at different times depending on what mode you are in. 2, 4 or 4Lo.

 

Also, I see that pin 4 on that 6 pin connector is ground. Does that go through the 4WD ECU to provide ground, or is it direct??? What I'm asking is; does the vehicle have to be running for me to see near 0 Ohms on that pin.

 

No, it doesn’t go through the 4WD ECU. I goes through 2 different connectors and eventually ends up on right hand side of the engine block on the 4.0.

Can I ask, why are you starting at the transfer case?

 

when you say “checked grounds”, what did tht entail? A visual look at a connector or wire can provide a false sense of security of its health.

 

It seems easier to me to start there as I don't have to take anything apart. If I have to go further and get behind the glove box, I will.

 

I understand that simply looking at a ground can be misleading, but I was just looking for something really obvious. Like I said, I will dig in on Sunday with a DVOM. Simply didn't have enough time today. Thank you for all the help, JP.

 

The ground for the limit switches is on the back of the passenger side cylinder head (Ground Point EE) so yes it would rely on the block ground being good, the ground for the 4wd ECU is behind the passenger side kick panel (Ground Point IE).
If you want to do a resistance check I would do it across the pins on the actuator with the connector unplugged, the truck doesn't have to be running to do voltage checks but the key needs to be in the run position.

Pin 4 of both the Transfer Case Actuator and the ADD Actuator go directly to Ground Point EE on the back of the passenger side cylinder head, there is a junction connector (PA) that they go through behind the glovebox.
I prefer voltage drop testing vs resistance testing to check ground integrity as it's more reliable.

 

it is difficult to get any readings from the transfer case connector because it’s a weather tight sealed connector, that’s why the factory troubleshooting procedure directs measurement at the input of the sensors to the 4wd ECU.

 

As long as you understand the with the exception of the ground wire, the others need to be checked with the plug connected. I personally would feel better back probing the 4WD ECU as the connector on the transfer case is “water tight” making it a bit harder to probe.

 

Up to you but I can literally have the glovebox and trim out in 30 secs, a single 10mm bolt is all that holds the trim in besides some plastic clips.

 

Understood, maybe I'll start there. Let you know what I find, Thanks again for the advice.