Rear Diff Lock Anytime Mod 3rd Gen DEVELOPMENT

I know the locker will unlock if truck is turned off .

Personally more interested in the 2lo mod than locker any time as if I needed the locker I'd be in 4lo anyways as that's where I always am when wheeling. And it keeps trans temps low.

I would really love the 2lo mod but not hacking the original harness . Which makes me want someone to make a pigtail harness .I know someone on here did it for the radio navigation thing so you can bypass the motion lock out etc by cutting the added in harness portion.

Just for the same of being able to revert back to stock for warranty cases.
Edit
It was @jshsltr that made that harness. Would be cool if he could do it again but for the 2lo mod

 

I am going off the info from OP where 77% duty cycle,(effectively 9.24V), brings it in, then 50% duty cycle maintains it. and those voltage levels delivered 4. and 2.0 Amps respectively. Then since disconnected from the vehicle, an integral monitor and make sure the diff is still engaged.
I would tend tp agree with you the coil can probably handle the additional current brought on by the 12 V supply. My thinking was to try and replicate the signal from the vehicle since that is presumably the design operating range of the coil.
With that, I refer to my earlier statement about convincing myself of a certain idea, regardless of the facts. It's very easy to get so invested in a concept that starting over or back tracking a bit never seems to be an option.

 

I would like to get away from the microprocessor but I just don't have the experience designing my own board to jump in on a project with my expensive truck. I work with PLC's too so it's just what I know. I don't like relying on software but I do program millions of dollars worth of equipment on those things so I'm confident in my abilities with it. I just don't necessarily trust an Arduino, I have a few PLC's with a blown channel or something so I might run that to start. They are pretty bulky but the smallest one I have is about half the size of my keyboard. I got a few other projects on the go but with winter coming, I want to lock it in 2wd in the deep snow and have some fun.

 

There would be a lot of guys who would buy this from you. Myself included.

 

In post #19 Diff coil is measured as 3ohms... so there's the answer for a resistor to spoof the 4wd ECU.

How many wires go to the rear diff ?

I see F12-1 and F12-5 are the pos and neg power going to the diff lock actuator.
F12-4 is power supply coming in to ECU.

Anyone able to ID which terminals are feeding the ECU with sensor info ?

I wonder if this mod can be done in the cab at the 4wd ECU with a 3ohm resistor across the sensor wires and switched 12v+ at F12-1 ???

Edit to add...

Is there a separate sensor in the rear diff feeding info to the ECU ?
Or is the sensing done inside the ECU when power is applied to F12-1

If you cut F12-1 and F12-5 at the ECU and bridge them with a 3ohm resistor, (on the ECU side) the ECU will think the coil is still there and unlocked.

That will leave the + and - wires (going to the diff) available for a manually switched 12v.

???

Here's a 3ohm resistor... (I just ordered one)

$7 LM YN 100 Watt 3 Ohm 5% Wirewound Resistor Electronic Aluminium Shell Resistors Gold (Pack of 2)

https://www.amazon.com/LM-YN-Wirewo...qid=1543625995&sr=8-9&keywords=3+ohm+resistor

 

Also another thought on the regulated voltage going to the diff lock from the ECU...

It's entirely possible Toyota found that applying 12 volts abruptly will create a loud annoying "CLUNK" that would make people bitch.
Regulating the voltage is another way to soften the engagement.

 

Presumably. I made a similar assumption in my work. If this is indeed true, a side effect would be that the dash board indicator would no longer be reliable. It would only work if you engaged the OEM button, and it would only mean that current was flowing through your shunt resistor. Your external circuit would need a "Circuit active" pilot, and that could be a separate indicator on the dash or an independent LED in the actuator switch

 

Yeah I came to same conclusion.

Also concluded there is no simple answer.

 

Would be nice if the factory momentary switch could be replaced with a simple on/off switch so we could hijack the wires from it at the ECU also.

 

I agree. This is what I was working with:

 

Do those switches share the same dimensions as the OEM switch for an easy fit ?

I'm not even worried about the dash indicator or Trac control/ABS. Would just love to have manual control of the diff lock... so a simple on/off illuminated switch would do the trick for me.

My 3 Ohm resistor wont be here till next week so I may need to just use a 12v jumper at the ECU to test until I source a viable switch.

 

They wont fit in the center dash. But they do fit the faceplates that are sold to let you put switches in the drivers side cubby. The ones I showed above are three position switches, but they have traditional 2 position ON-OFF configurations too.
The good news is that, through Rocker Pros, you can get almost any custom actuator you want. The bad news is, since they are rocker style switches instead of pushbutton, you either need to use the drivers side cubby with a switch cutout face plate of some sort, or cut square hole somewhere in your dashboard or center console.

 

Ugh.
Maybe we can use a relay/contactor between the OEM switch and the ECU ?

 

OK. first thought is, if you have already bypassed with a resistor, the factory switch is essentially useless in its current configuration. Is the switch part of the ECU diagnostic circuit? I am guessing not, But I am not certain. If it is just an actuator, sever and secure all the wiring connections except the power for backlighting and its ground. Then determine which wires are associated with normally open and normally closed connections, and connect accordingly to the relay.
Edit: Assuming the resistor is upstream of the switch

 

Of course there is the old 12 mm round pushbutton that lights up when it is "on"

 

No, the diff lock un plugged isnt the only thing that throws a code.
Diff remaining locked while uncommanded also throws a code.
(Just as an example of additional items to consider)

 

Recommended incorporating 2LO only because it is easy to do while in the 4wd harness... (same connectors and wire bundles at the 4wd ECU). I developed my 2Lo mod first, then looked at anytime lock because people were requesting it. I never really cared as much for it, reason it never got completed while 2lo is fully tested

 

As soon as I get some time away from the honey-do list and my 3ohm resistor arrives, I'll dig into the F12 connector and let some smoke out of the wires.

 

Connectors have been identified (not yet tested), so you can make your own harness.

See very helpful work by up2nogood
https://www.tacomaworld.com/threads...d-gen-development.537810/page-8#post-18502251
And a second post a little further on.