Possibility of having 4L without center diff lock?

[Jellyfish Junior Member 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 Junior Member 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 Junior Member 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 Junior Member 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

[Jellyfish Junior Member Find all posts View Profile Close Jellyfish]

Apologies if it takes so long to update this. Just an update on what I`ve managed to find.
Upon attempting to trace the cables from the H4F / H4L / L4L rotary selector switch, I`ve noticed the wires from behind the rotary switch which also have the following, Green, Violet, White with Black line X2 and Pink wire from the connector.

I`ve also tried to de-pin only the pink wire from the connecter, and reconnect the connecter and ran a test, to see what will happen.
Result: switching from H4L or L4L have no issue, but upon attempting to return the rotary switch the CDL and Low Range icon still remains until I`ve reattached the pink wire back into the connector. then the selector managed to switch off the CDL and want back to H4F mode.

Now I tried to de-pin only the violet wire from the connecter, and reconnect the connecter and ran a test, to see what will happen.
Result: switching from H4L or L4L have no no response, no CDL or Low Range icon was observed. Only after reattaching the violet wire back, the selector can now shift to H4L and L4L

I stopped messing around with the wires and installed the panels back(which can be removed relatively easily.

Only wire I did not touch was that 2 white wires with black lines on them. Maybe it does not work because I missed out something with regards to what ptommo59 have advised.
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.

Do I need to swap the 2 White with Black line wires?

BTW those pins on the connector is sure a PITA to remove, lol

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

Thats the wrong connector, that dash 4WD Transfer Position switch connectors' wires won't help you as anytime the Grey wire (your Violet in pic) is earthed the centre diff lock will be enabled by the 4WD ECU.
The Pink wire when earthed selects High Range and when not earthed allows switch over to Low Range when Grey is earthed.
The white with black stripe wires are both earths one for the switch and the other along with the green wire are for switch illumination when lights are on.

To achieve what you were after you need the wires to the connectors for the 4WD ECU (the two are shown in pic looking at front of the harness side connectors, with 40 Pin one being G53 and smaller 10 Pin one G54 (pins highlighted are the ones listed in earlier post).

[Jellyfish Junior Member Find all posts View Profile Close Jellyfish]

Thats the wrong connector, that dash 4WD Transfer Position switch connectors' wires won't help you as anytime the Grey wire (your Violet in pic) is earthed the centre diff lock will be enabled by the 4WD ECU.
The Pink wire when earthed selects High Range and when not earthed allows switch over to Low Range when Grey is earthed.
The white with black stripe wires are both earths one for the switch and the other along with the green wire are for switch illumination when lights are on.

To achieve what you were after you need the wires to the connectors for the 4WD ECU (the two are shown in pic looking at front of the harness side connectors, with 40 Pin one being G53 and smaller 10 Pin one G54 (pins highlighted are the ones listed in earlier post).

Ahhh, icic, back to the drawing board to track that 4WD ECU and the connecting pins.

Was thinking of how to access the 4WD ECU without me tearing out too much things and breaking unnecessary clips along the way.

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

You should be able to access the 4WD ECU by removing the glovebox and lower trim.

Make sure you disconnect battery negative before disconnecting 4WD ECU connectors as constant battery power goes to the ECU for memory power retention.

[Jellyfish Junior Member Find all posts View Profile Close Jellyfish]

You should be able to access the 4WD ECU by removing the glovebox and lower trim.

Make sure you disconnect battery negative before disconnecting 4WD ECU connectors as constant battery power goes to the ECU for memory power retention.

Thanks for the heads up, I was kinda worried as I was thinking if I need to remove my head unit and all other equipment installed there to access the 4WD ECU.

Lemme find some time to fiddle with this.

BTW, I was studying you previous instructions
* 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);
Does it mean I need to swap both the wires?

* CDL Detection Switch line (CDL/P1) to be earthed.
Errr, kinda lost here, do I extend and connect the wire to the chassis ground?

Apologies if I sound like a noob here (I am) only handy with mechanical stuff, but kinda clueless on electronic issues.

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

Start by just open circuiting one of the motor TM wires (if you can use an inline switch so you can open circuit and also reconnect) and see what it does when you switch to low range (L4L), drive for a short distance and then switch back to high range (H4F) and reconnect the TM wire again.

It should change ranges but give you a P17DE DTC to indicate the CDL motor is open circuit/not drawing current but if the code clears by itself when you go back to high range and reconnect the TM wire that would potentially work for what you are after (may need to also switch to Low range and back to help clear the DTC).

If the DTC doesn't clear automatically then you need to decide whether to manually do it with a scantool or look at also doing the position switch change over on the other connector as well which will be more complicated.

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

The other place you could disconnect the TM wire is at the 25 pin connector CG2 also behind the glovebox

[Jellyfish Junior Member Find all posts View Profile Close Jellyfish]

Start by just open circuiting one of the motor TM wires (if you can use an inline switch so you can open circuit and also reconnect) and see what it does when you switch to low range (L4L), drive for a short distance and then switch back to high range (H4F) and reconnect the TM wire again.

It should change ranges but give you a P17DE DTC to indicate the CDL motor is open circuit/not drawing current but if the code clears by itself when you go back to high range and reconnect the TM wire that would potentially work for what you are after (may need to also switch to Low range and back to help clear the DTC).

If the DTC doesn't clear automatically then you need to decide whether to manually do it with a scantool or look at also doing the position switch change over on the other connector as well which will be more complicated.

Thanks ptommo59 for the clarification, I`ve gotten an inline switch already, only will do the wire cutting upon confirming the proposed TM wire hack works first and can be reinstalled back good as new without any damaged of codes.

I am running a Scanguage2 since I`ve gotten the car, loving its simplicity.

Will report back in due time on this hack, as this beloved Prado is my daily driver, I`ve gotta carefully plan when I can perform this and also give me enough time to rectify any cock up, due to my inability or lack of talents, lol

Kinda miss Aussie environment, with excellent service and support over in land down under. Back in Singapore, Prado, Fortuna, 200, 300 series, or any other 4X4 is rare, due to our tax structure which dose not support fuel guzzler 4X4, as such there is basically no market to allow a trained mechanic to be fully handy in providing any modification such as this, most of the time it is just a sloppy job.