Rear Diff Lock Anytime Mod 3rd Gen DEVELOPMENT

Good luck
Most of the data needed to do the design the needed circuits is buried in this thread. Most of the schematics are buried here before you go smoke anything.

Good luck guys, I know there is alot of interest if you guys make it happen.

 

Manual hubs?
I didn't see any on warn's site but I'm interested, if you have aline pease post it.

 

Here is a link to the latest thread I have been reading through.
https://www.tacomaworld.com/threads/free-wheel-hub-conversion-3rd-gen.513930/

 

Found a latching relay on Amazon that looks like it will work with the OEM momentary switch in the overhead console.

KNACRO DC 12V 1 Channel Self Locking Relay Power Control Module Two-Button ON/Off Maximum Load AC250V / 10A DC30V / 10A with External Trigger Switch Socket and Connection Wire

https://www.amazon.com/dp/B01J0SQQE6/ref=cm_sw_r_em_apa_i_xWPaCbK8G19J1

Once the wires from the switch are identified at the ECU, they can be used to trigger the latching relay... which can power the diff actuator.
Push button once to activate, push again to deactivate.
So... no need to replace the overhead console switch.

Make sense ?

 

You may have to play with the set up to make sure you get the trigger,(OEM button), working the way you want. Then find a way to make sure the toggle on the PCB is protected from getting pressed or bumped once installed. Otherwise you might get the diff. permanently locked and not know why since it won't disengage when you press OEM button to disengage

 

So you guys are assuming that you will disable the ecu system of locking completely?

Btw
Here is the electromechanical solution that I posted way back in the thread. This design assumes that the original ecu button and ecu controller would be maintained.

 

That was not my approach. Mine was to retain it to work as intended, and then install a bypass circuit with its own switch and PWM in line, for when you wanted to run it when the ECU didn't want to let you.

What @Dragracer_Art is looking into, is to unplug the diff coil from the ECU and put in a shunt resistor to fool the ECU into thinking it is still plugged in. Then, repurpose the OEM switch to activate a relay that would supply voltage directly to the diff coil.

 

It would be nice if we can figure out what component in the 4wd ecu is blocking the locker under certain circumstances and just bypass that. Anyone think they can look at a wire diagram and the 4wd ecu to reverse engineer a logic diagram? I would think if the logic diagram can be figured out then bypassing the locker blocker wouldn't be that hard, right? Or am I over simplifying this?

 

I do know, I over complicated my initial approach. I need to step back a little and re-engage with a fresh perspective. Also, I think I will wait until I can get a good look at the wiring in the vehicle. Get to knw where things are, how accessible, and what the "real-estate" limitations are when it comes to implementing.

 

That's essentially what I was trying to do, without actually knowing what I was bypassing. I was just going to introduce a pulse signal, down stream of the switch, to the coil while temporarily applying the dummy resistor upstream. this would let the ECU thinks its still plugged in but not active. Then when by-pass kicked out, the original OEM circuit reconnected to operate per Toyota protocols.

Edit: reference to PDF in Post #226, Basically it would drop in at connections 6,12 on EB1 , (or connections 3 and 6 of BD1). Essentially right at the coil

 

I tried hard to figure it out originally.
The same 4wd ecu is used in a 2wd OR truck, and will lock anytime.

The 4wd ecu knows from canbus that it is installed in a 4wd truck. The 4wd ecu wont engage locker unless it thinks the truck is in 4lo. For that to occur, multiple sensors in ADD and transfer have to be spoofed, as well as the 4wd switxh in dash in 4lo.

I 100% believe its feasible to go this way if enough effort is expended

 

Thank you for explaining that.
Thats exactly what my thoughts are.

I did order the latching relay... so sometime next week I'll have a resistor and relay to tinker with.

Which raises my next question... Where is the 4wd ECU located in the truck ?

And... has anyone deciphered what pins at the ECU are connected to the momentary switch in the overhead console ?

I feel like this entire bypass procedure can be done right at the ECU for under $20.

 

Yall are some smart mf'ers. Thats all I can add.

Mostly just posting for updates but also to say, yall are some smart mf'ers.

 

Matt with @OVTune has figured out how to hack into the Toyota computer... I wonder if he can get into or access the 4wd ECU through the OBD port ?

 

I am inclined to think that the locker blocker... That's what I'm calling it by the way... I'll coin the term now, "locker blocker". I think it's probably hardware built moreso than software. If it's hardware then I would also think that it's a logic gate that needs its series of "1's" in order for the output to the locker to be a "1".

Im not even sure this is how the 4wd computer is built, but if it is a simple system then if someone can reverse engineer it then getting around the locker blocker shouldn't be too difficult. I just don't know enough about circuits yet to decipher the circuit board.

 

For 4WD ECU, see my 2 wheel lo mod instructions. Full access steps to get to the ECU is given in the instructions
https://www.tacomaworld.com/threads/lock-stock-and-2wheel-low-3rd-gen-diy-mod.536677/

I already attached all the ECU wiring I believe Specifically see this thread post 221. See also Post 8
https://www.tacomaworld.com/threads...-gen-development.537810/page-12#post-19268237

 

Is there a way to make the truck think it's in 4Lo while being in 2Hi? This would make activating the rear diff lock possible without fooling with the safeties built into the rear diff locker.

 

Yes, it is believed to be doable.
Per my research without changing ECU internal codes you would have to do this:

You have to have have the dash switch in 4lo, or spoof the switch diodes.
You have to spoof the ADD position sensors (3 separate sensors)
You would have to spoof the transfer case position sensors (5 sensors).

I would also recommend removing the power to the add and transfer case, so bypass those with resistors.

Note, the truck would then think it was in 4lo and would activate the locker. Note, truck would be using the 4lo ecu mapping, rather than normal mapping. It may shit a brick if you go 60mph in 4lo, just dont know

If I get around to it, I will draw up a schematic for this option

 

Latching relay and resistor showed up.
Not sure when I will get time to mess with it.
Looks like relay needs two triggers... one to latch, one to unlatch. I thought it worked differently so may need to rethink how I want to wire it so the factory overhead console switch can be used.

 

Not much new to report here. Had a few minutes after work today to pop in some LED interior bulbs and snapped a pic of the rear diff lock plug/wiring just for reference.
Looks like it all dumps into a plug on RH side of circuit board.
The main overhead harness plugs into the left side of the circuit board. Starting to wonder if there is actually a direct wire from the overhead diff lock switch to the 4wd module in the dash... or if there is some kind of communication between the boards instead. Didn't dig any further into it. Weather has been real shitty lately and wife has been sick.