Possibility of having 4L without center diff lock?

[Jellyfish Lurker Find all posts View Profile Close Jellyfish]

G`Day guys, I`m been trying to search for ways to bypass the auto center diff lock on my 2.7liter petrol driven 2020 Prado, as my model only have a rotary dial with 4H - 4H Locked - 4L Locked, that`s it nothing else.(Refer to attached picture)

The reason behind it is occasionally I need to drive up a series of very steep sharp hairpin turn on concrete driveway fully loaded with gears, and I do need to carry a lot of speed on 4H in order to generate enough momentum, but that puts everyone at risk in that silly speed. If I were to use the 4L Locked, the center diff will automatically comes on, and performing the hairpin turn on high friction surface it not something I am comfortable with, knowing the end result might be self destructing of the gears.

I did come across certain years of Prado with a rotary dial but it comes with an optional diff lock button. (Refer to second picture)

Is it possible to hack something out to manually activate the center diff or any other option available? As its is a very awesome vehicle to drive in, and the only flaw I can find on this beloved vehicle is only this auto diff lock issue.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

I did a quick check on the 4WD System description and wiring diagrams and its doesn't seem it can be done just by changing out the switches as the 3 Mode in yours uses different 4WD ECU inputs to control the HI/LO Range and Centre Diff Lock functions to the 4 Mode (with LO Unlocked). So it would also require integration of a different 4WD ECU config or reprogramming of yours if it can be made compatible with the 4 Mode switches.

There may be some way via wiring/switches to disable the activation of the center diff lock in H4L and L4L but that would also require fooling the 4WD ECU into thinking it had activated or it would trigger a fault code (so also not a simple switch setup).

[Jellyfish Lurker Find all posts View Profile Close Jellyfish]

I did a quick check on the 4WD System description and wiring diagrams and its doesn't seem it can be done just by changing out the switches as the 3 Mode in yours uses different 4WD ECU inputs to control the HI/LO Range and Centre Diff Lock functions to the 4 Mode (with LO Unlocked). So it would also require integration of a different 4WD ECU config or reprogramming of yours if it can be made compatible with the 4 Mode switches.

There may be some way via wiring/switches to disable the activation of the center diff lock in H4L and L4L but that would also require fooling the 4WD ECU into thinking it had activated or it would trigger a fault code (so also not a simple switch setup).

Thanks for your attached file which provides much clarity to the electronic set up, guess there is a lot of differences between both models, let alone mine is a 2.7liter Petrol variant.

I`ll do some more research to see if any local boys in my area dare to take up the challenge to modify the electrical system without triggering the fault code just to interrupt the signal from the transfer case that tells the locked ECU that it went to low range but is still sending a signal to the transmission ECU telling it is in low range. Therefore the transmission will shift in the correct low range pattern. Just to have true manual control over center diff locking.

The only nearest solution I`ve seen is from a site in USA documenting the procedure involved, but not sure if my car runs the same set up as the vehicle indicated in the site in the link below.

https://sleeoffroad.com/center-diffe...ock-pin-7-mod/

Will update once I`ve tear out the side panel to locate the transmission control relay.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

That link seems to be for an 80 Series Landcruiser or Lexus LX450. The relay mentioned is not part of the current generation systems as its all controlled from the 4WD ECU as per the diagrams I posted.

To stop the CDL from actuating and fool the ECU to thinking it had would need:

* one of the wires (TM1 or TM2) to the CDL actuator motor to be open circuited;
* the unlocked and locked actuator limit switch (TL2 and TL3) states to be reversed (the CDL light would normally flash when one or the other is not earthed e.g. when the actuator is in motion); and
* CDL Detection Switch line (CDL/P1) to be earthed.

The attached wiring diagram extract has the pin and connector numbers that should match your config (as it hasn't changed since Aug 17).

You could try just doing the first TM1 or TM2 item and see how it reacts i.e. will it allow you to drive in LO but set a failed CDL actuator/motor DTC but auto clear this when you put back to normal or do you also need to manually clear the code.

[Jellyfish Lurker Find all posts View Profile Close Jellyfish]

That link seems to be for an 80 Series Landcruiser or Lexus LX450. The relay mentioned is not part of the current generation systems as its all controlled from the 4WD ECU as per the diagrams I posted.

To stop the CDL from actuating and fool the ECU to thinking it had would need:

* one of the wires (TM1 or TM2) to the CDL actuator motor to be open circuited;
* the unlocked and locked actuator limit switch (TL2 and TL3) states to be reversed (the CDL light would normally flash when one or the other is not earthed e.g. when the actuator is in motion); and
* CDL Detection Switch line (CDL/P1) to be earthed.

The attached wiring diagram extract has the pin and connector numbers that should match your config (as it hasn't changed since Aug 17).

You could try just doing the first TM1 or TM2 item and see how it reacts i.e. will it allow you to drive in LO but set a failed CDL actuator/motor DTC but auto clear this when you put back to normal or do you also need to manually clear the code.

Wow, I was wondering where you get these diagrams from, I`m not trained in electronics and stuff, and seems beyond my depth of knowledge to understand. Guess I`ll stick to more mechanical stuff, lol

Let me bring the list to my local sparkie to test their knowhow, hopefully it all works out well without the error code.


In the meantime, I might need to source for a on/off switch to manually engage the CDL when the terrain really calls for a CDL to come online.

But what is the repercussion if I would to just keep TM1 or TM2 in open circuit and have it connect to a on/off switch without touching the rest of the wires, I foresee the following scenario

1) CDL is in open circuit, switched off via switch and an error code will flash out on the dash (god knows where) and I can either wait for the error code to clear itself when back to normal drive mode or use my scanguage2 to manually clear it.

2) CDL is in open circuit ,switched off via switch and an error code will flash out; until toggle switch is switch on which will close the circuit and vehicle center diff is locked.

Now, lemme go find where is that Transfer shift actuator is located, and track where the wires runs to inside the cabin, as I prefer the removal of signal from inside the cabin away from the nasty environment.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

The transfer shift actuator assembly is the black box mounted on the rear of the transfer case so you would be better off using the 4WD ECU end wiring (The 4WD ECU should be behind the glovebox on the console side and have a part no starting with 89533-#####).

From the previous diagram you are looking for:

TM1 - Connector G54 Pin 7 (Purple wire)
TM2 - Connector G54 Pin 8 (Pink wire)

TL3 - Connector G53 Pin 10 (Green wire)
TL2 - Connector G53 Pin 9 (Purple wire)
P1 - Connector G53 Pin 3 (White wire)


The attached picture show the pin connections as viewed from the bottom of the 4WD ECU (or backside of the two connectors).

[Jellyfish Lurker Find all posts View Profile Close Jellyfish]

The transfer shift actuator assembly is the black box mounted on the rear of the transfer case so you would be better off using the 4WD ECU end wiring (The 4WD ECU should be behind the glovebox on the console side and have a part no starting with 89533-#####).

From the previous diagram you are looking for:

TM1 - Connector G54 Pin 7 (Purple wire)
TM2 - Connector G54 Pin 8 (Pink wire)

TL3 - Connector G53 Pin 10 (Green wire)
TL2 - Connector G53 Pin 9 (Purple wire)
P1 - Connector G53 Pin 3 (White wire)


The attached picture show the pin connections as viewed from the bottom of the 4WD ECU (or backside of the two connectors).

Thanks ptommo59 for the assistance!!!! will find some time to see if this side quest is within my capabilities.
Will update this thread