3rd Gen Multi-Function 4WD ECU Spoofer

For clarification on my implementation of anytime locker, I will not be spoofing the truck to think it is in 4Lo, only sending power to engage. I know in the original thread @BigWhiteTRD expressed concerns about using lockers outside of the Toyota specifications (for example, in 4Lo, speed limited, ABS disabled) but as I sat with my thoughts for a few weeks, I came to the realization that many folks have put aftermarket lockers on their trucks, which are totally independent of Toyota limitations, and I don't think there's really an issue to worry about as long as people understand what they are doing. And if they're doing a mod like this, surely they will know, and I'm coming up with a way to ensure they know proper usage before they start using it.

I have a 2016 OR, but I don't think there's any difference, and my testing has shown the same result.

And great info! I knew it was PWM and have the duty cycle from Techstream & the factory service manual, but haven't had a chance to hook up a scope and determine frequency, so thanks for that!

Technically, it would be possible to create every function I plan to implement with timer ICs and other various components, but I made the decision from the beginning of my research that I would use a microcontroller because it just takes away a lot of the design time, particularly as things go to the trial and error phase. I mention this because any microcontroller I would choose would have PWM available on the GPIO, so to drive the locker it's as simple as placing a MOSFET on the board and sending it PWM. I wouldn't be brave enough to send constant voltage on my own truck and risk damaging or prematurely wearing out the coil, and even more so wouldn't feel right shipping that to anyone.

This is VERY cool. I'm not totally sure based on that post where you tied the blue LED, but it would be easy to tie into my board if you aren't driving it from T13. This dash mod would be outside the scope of this project, but for those with the skills, an easy add.

Without a doubt this will be mocked up on a breadboard before PCB samples are ordered!! And I'll definitely be sending pictures of that madness when I get it put together, it will be a doozy.

The schematic is wild at this point due to all of the different mods being a part of the same board. I made individual schematics for each mod first that you might enjoy perusing.

 

I’m on my 2nd ADD actuator and my replaced T-Case Actuator has finally fully shit the bed. After the T-case actuator went out last January, the replacement “worked” but would still throw intermittent 4x4 failure CELs…the frequency of these failures kept increasing from 1x every months or so to every couple weeks, the weekly, then daily and has now been on fully again for the last 3 weeks.

I have the FJ case from an auto arriving next week along with the 12th state ADD switch, really looking forward to seeing your spoofer come to life. Seems this will address most of the pitfalls of this swap.

 

@3pdltrd In the meantime, make sure to keep the actuators connected and zip tied up like @jcat2435. I read about guys doing that in the FJ swap thread and had a good chuckle, but while its funny to me, it’s quite effective!

 

@tcmd I’ll make sure to keep both actuators intact, bagged and secured out of the way haha. It is ridiculous but at least it’s an effective temporary solution lol. Thanks again for you efforts on this endeavor and truly looking forward this spoofer. I have had to cancel far too many trips due to losing 4WD randomly while driving around town in 2H.

 

Commenting so I don't lose the thread again

 

@tcmd do you know what you’ll need to employ on each circuit for the ADD spoof? That is really what I want to do more than anything for the time being since it’s easiest to install (FJ tube) and it’s the part that is slowest to shift and most likely to fail. I’d be okay with the electric shift t-case for the most part, at least for a while if I could just get rid of that damn ADD.

Certainly still interested in the spoofer but I wonder if I could defeat it with a relay and resistors similar to the 2 lo mod? I know I could do so from 2Hi to the 4wd modes, but it’s the going back to 2Hi that I’m not sure about. That’s the one that causes errors if you don’t forget to unclick the 2lo switch when shifting back. So to delete the ADD, I’m wondering what will be needed…

Could just zip tie the ADD up to the fender in the mean time but would like to know a good solution can be utilized eventually. Which the spoofer box will be good for but also good to know if there are other simpler options just in case like the relay mentioned above.

 

Actually yes, I believe you could just implement the 2LM as your ADD only spoof. From what I remember, the existing 2LM that @BigWhiteTRD came up with essentially just spoofs the ADD changing positions. You’ll be spoofing it and it’s already locked, whereas the original intent was to not engage the ADD and leave only the rear drive wheels.

It wouldn’t be as elegant as the microcontroller following your mode changes and taking care of the rest, but it would get you away from zip ties and a floppy actuator!

https://www.tacomaworld.com/threads/lock-stock-and-2wheel-low-3rd-gen-diy-mod.536677/

Somewhere in the thread, he explains the challenges with just using resistors & relays, but I’ll summarize it this way:

The 4WD ECU & main computer are looking for a series of limit switches to be activated in a particular order and within a particular time frame before it just gives up and flashes forever. It also monitors the current going through the actuator motor to make sure there isn’t an open circuit or a short.

So, it will require a timer chip (like a 555) or a microcontroller to create that series of limit switch changes and a resistor can be used to emulate the actuator motor. I’ve chosen to go the route of a microcontroller based system because it will allow for the most flexibility and greatly decrease development time on the electronics side. There is unfortunately no simple & easy way around this type of system because there are multiple switches and a defined sequence, which are all triggered by the 4wd mode knob being changed. Even the 2LM falls slightly short of the simple and easy standard because of having to operate a separate switch and do things in the right order, just like you mentioned.

 

I’m wanting to be able to install something that I can plug in and forget about, so no switching involved, etc. just wondering if I could make a relay do that for me, but I still don’t really understand what the 4WD ECU is looking for from ADD when in each mode.

Ultimately the spoofer box would be the most slick but probably makes more sense when I decide I want the tcase too down the road.

 

Tacoma owner’s fault. Truck is filty with sand crap, or whatever crap.

 

@BLtheP The ADD is simpler than the Transfer case and a relay does work for the limit switch spoof. For the ADD basically there’s a switch to signal “hey I’m locked” vs “hey I’m unlocked” and it is 2 separate switches.

The tricky part is how to engage and disengage the relay without a separate switch.

The obvious choice of switch is the factory 4wd select knob, since you’ll be wanting to change the 4wd mode at the same time that the spoof is engaging/disengaging. This would not be straight forward since the knob has 3 positions, but it has a circuit inside that drives only 2 wires back to the ECU. Additionally, it selectively pulls these 2 wires to ground, not up to 12V, so you wouldn’t be able to drive a relay with only these wires, it would need additional circuitry. There are some integrated configurable relay driving boards available via retail, so this might be somewhat doable if you want to find one.

I’ll post a simple schematic from the factory service manual that will explain better for those that can follow circuit diagrams. However, the 2LM development thread does have the ADD diagram if you want to look at that to start trying to wrap your brain around the circuitry.

 

$9 AEDIKO 4pcs DC 12V Relay Module 2 Channel Relay Board with Optocoupler Support High or Low Level Trigger

https://www.amazon.com/AEDIKO-Chann...&sprefix=relay+board+pull+down,aps,224&sr=8-1

This is an example of the type of configurable relay driver I was talking about, but I’m not 100% sure this would work without side effects since you’d be feeding voltage back into the the select knob circuit to use the pull down configuration of the relay board.

Far from plug and play, but if you want to try it out, go for it!

 

@tcmd thanks for all the info, very helpful. If you want me to move to PMs for further discussion so I don’t clog up the thread with not quite spoofer module related content, let me know. I wouldn’t mind having a group with you and bigwhitetrd to work through the details lol.

I have done quite a bit of digging but am still wrapping my brain around it. The way I understand that 4wd switch is that ground is pulled on pin 2 only for 2wd, both 2&3 in 4hi, and only 3 when in 4lo? If I have that correct, I think pin 3 could be my ground trigger for a relay possibly and use a SPDT relay? The way I understand it (from this thread - 2nd gen but seemingly the same ADD operation as ours) is that there are 6 wires at the ADD:

1 - red - motor control (12v or ground)
2 - light blue - motor control (12v or ground)
3 - blue - “ADD” - tells the Skid control and 4WD ECUs when ADD is engaged (in 4wd)
4 - black/white - ground
5 - pink - limit switch (to confirm ADD engaged (4WD) (not sure what the difference between this and pin 3 is besides this one not relaying 4wd status to the skid control ECU like pin 3 does)
6 - green - limit switch (to confirm ADD disengaged (2wd))



the operation as it seems to me is that anytime the motor is shifting, the red and black wires are energized and grounded. I believe it will provide power on red and ground on black in one direction, then flip them for the other direction? Kinda like a power door lock?

So I’m pretty sure I would just need a permanent resistor across 1 and 2, like the 2lo mod adds (to fool the ECU into thinking the ADD is still there) and then….

For tricking the rest of the ADD operation, it looks like pins 6 and 4 (ground) are connected in 2wd, and then in any 4wd mode pin 6 disconnects from the ground (pin 4) and instead, 3&5 are connected to that pin?

so I’m thinking I could use the following relay setup:

86 - ign
85 - ground from pin 3 @ 4wd switch
30 - ground (to act as the new pin 4 from ADD)
87A - pin 6 from ADD (always connected to 30 until shifted)
87 - pin 3&5 spliced together, possibly with diodes to prevent them backfeeding each other if that is necessary

if I understand things right, starting the truck would be in normal 2wd mode, and pin 6 would be connected to ground via the relay, like a normal truck in 2wd. Shift to 4hi with the knob and pin 3 should trip the relay which then connects ADD pins 3&5 to ground as if the motor was in 4wd?

Am I missing something? The only problem I can think of (unless I’m misunderstanding how the knob works) is that if I parked the truck and shut it off in 4wd, when I turn the truck back on (still in 4wd), I wonder if a failure would be detected if the 4wd ECU sees anything appear weird the split second before the added relay switches? Not sure. Maybe it would be fast enough to be fine. I mean, the 2lo mod always worked okay if you shut off the truck in 2lo. So I think it would work, but testing would be needed…

I was thinking there might be some problems with the 4wd ECU not liking that the ADD was “done shifting” (via the relay switching) before the transfer case has completed its shift, since they are supposed to follow a sequence where the transfer case shifts first. But I think the 2lo mod has proven that to not be a problem. It doesn’t seem to care what does what when as far as the ADD is believed to have shifted.

 

Yeah, god forbid someone actually take their 4x4 pickup out into the wastelands where's there's mud and dirt.

I can't tell if this was a pointless response, or mine is.

-Related-

Thanks for all the discussion in this thread. It's been bookmarked, because it's really providing some good discussion on how the system functions for anyone out there having issues with their add/xfer case actuators, it's surely a goldmine.

 

I was talking about person in YouTube video. Water got into ADD, lucky dealer replaced actuator under warranty the first time.

 

@tcmd Sorry for not commenting on your Post #61, I had more than a bit written as a comment, however that was deleted by the system.

Yup, that additional circuitry is two diodes.

The factory 4WD Knob can be used to drive a relay coil with the use of two "Steering" diodes. I have no drawing software so this can be tedious to follow for those not familiar with some basic-old-time-electronics. In this description I will use "Anode" and "Cathode" to describe the ends of the diodes.

-Open the purple wire at Pin 13 of connector F13 of the ECU, insert a diode with the Anode towards the ECU and the Cathode towards the 4x4 F15 Switch connector.
-Connect the Cathode of a second diode to the first diode's Cathode; connect this second diode's Anode to one side of the 12VDC relay coil and the other side of the relay coil to a 12VDC supply.

Please draw this out on paper to see its operation. The use of Steering Diodes keeps the 5VDC logic levels away from the 12VDC power and vice-a-versa. For those reading this that do not know what an Anode or Cathode is see: Diode - Wikipedia

This comment is only to address the use of the 4x4 Knob to be able to energize a relay coil, not any other problem with fooling the other parts of the circuit(s).

I think you have it quite right. Not at all sure it will only be a SPDT relay.

You both (BLtheP & tcmd) mention power failures and the 4x4 system possibly disengaging certain functions of the system. I would like to suggest with the final spoof circuitry that Pin 4 of F12 be held high at all times the 4x4 system is in use. This would be particularly advantageous in a Manual Transmission where stalling of the engine is more often encountered during difficult obstacles.

 

I’m really not thinking much work will be necessary to use the knob. To my understanding, pin 3 will be grounding the 4wd ECU pin 13 on the B connector anytime the ADD should be engaged. Therefore it seems to me like that could be the relay trigger. Of course with the relay also getting ignition power from somewhere to complete the relay coil circuit.



The rest of fooling the ADD would be a resistor to spoof the motor itself and then it should just be a matter of the relay grounding the right wires (the limit switch wires) in NC and the other limit switch wire in NO

 

How about old school? Get a non-4x4 system replaced in the Taco and everything 4x4 manual. Manual (air)locking hubs, FJ transfer, etc. No lights or ECU getting in way of driver's choice selection.

 

I would like that but don’t get the built in features like ATRAC and locker and whagever else if stuff isn’t spoofed. I do like the lights though….

not sure of a good hub solution these days, haven’t seen any options. I probably prefer always engaged unit bearings like we have over locking hubs although the hubs do have their benefits for sure.

 

ATRAC is controlled by Skid Control ECU (Brakes), for Locker ARB has air controlled kind. Hubs is another lost item...