3rd Gen Spoofer Development for ADD and Transfer Case Actuators

Ever since I bought my truck, I have wanted to swap both my transfer case to a manual shift case out of an FJ or 4Runner, as well as delete the ADD actuator and run a fully live front diff that is always ready to go as soon as the transfer case shifts to 4WD.

I held back from both projects for a few reasons, the main reason being that it can be tricky to get rid of the actuators and have the 4WD ECU not freak out on you. Nobody truly came up with a way to make the manual transfer case take over for the electronic case and maintain all the signals the computer used to see from the actuators, so I thought it just couldn’t be done. If you just unplug the actuators, you get a bunch of 4wd failure warning lights and then yo can’t access your features like A-TRAC, MTS, Crawl Control, and the locker.

Curiosity for the best of me, and I started experimenting. I’ve finally figured out how to spoof both of the actuators with a wiring harness that plugs in at the 4WD ECU. This will be in several parts. The first part will be about a harness that only deletes/spoofs the ADD. There are many here who would be fine with just an ADD deletion while keeping the electronic transfer case. I think the transfer case is significantly less problematic than the ADD, so to me the ADD was the one I really wanted gone. However, manual cases are awesome and I know of a few who installed them here who currently just have the actuators zip ties somewhere still running off the knob. There is now a discovered solution to get rid of that. I’m going to make subsequent posts, one for ADD and one for the transfer case.

Ultimately, what is required to spoof both actuators is a harness that includes 6 relays and 2 resistors I actually have been testing the ADD without a resistor and it is working perfectly fine. I will be testing the transfer case harness without a resistor soon and will report back on what happens. I’ll outline the functions of the relays in later posts.

Testing for the ADD actuator delete:



Testing for transfer case actuator delete (ADD delete also included in this one):



I’m going to reserve a few posts after this so I can talk in detail about the ADD spoofing, the ADD delete itself using the FJ tube, and the transfer case delete.

I have confirmed that with the full transfer case delete harness, we can completely spoof the transfer case and have 100% stock functionality with no knob needed. Everything actuates simply off of the two transfer case switches on a manual transfer case.

If only doing the ADD delete, I have confirmed that doing so works perfectly fine as well. You turn the knob to 4H, the computer immediately shifts the transfer case (which shifts very quickly), and the indicator comes on immediately because you’re no longer waiting on the ADD to move - the ECU sees our spoofed feedback and thinks all is well.

Lots of info to get into words, so it will take me some time. I’m also going to try and make some visual wiring diagrams to make it easier to understand.

Stay tuned!

 

ADD Electrical Spoofing:

I started all of this exploration by looking into the ADD delete, since this is what I personally wanted for myself more than anything. There are two very helpful threads on these topics from the 2nd Gen forum:

Deleting the ADD mechanically (I think initially written by @6 gearT444E ?)

https://www.tacomaworld.com/threads/how-to-deleting-add-system.427258/

This write-up is spot on for us 3rd genners. It is about making the physical change that gets rid of the ADD motor entirely and replaces the old ADD motor and tube with a solid tube and axle intermediate shaft that has a direct connection to the differential. I am only mentioning this thread in this post because it helps with understanding what the wiring is for. The computer will not be happy if you simply unplug the ADD as part of the physical ADD delete, so you need to read the wiring below to keep things happy.

Note: This will make the front diff spin 100% of the time (anytime the front wheels are rolling). This does NOT put the vehicle in 4WD, you still are disconnected front to rear in the transfer case, and so the front and rear can differentiate from each other. This just means the front diff, driveshaft, and trasnfer case will now be spinning at vehicle speed.

This does not mean you're going to start wearing out parts quickly. Making the parts spin is not going to ask the parts to do more than they are designed to do. You may lose a tiny bit of fuel mileage, which is why the ADD is there to begin with. The ADD doing what it does stops some parts from spinning which helps fuel mileage a little bit. Otherwise, there are no real downsides to losing the ADD. The only potential other downside is no longer having the ability to use the 2WD Low kit that is popular here. Other methods to achieve 2WD Low, would be to install a twin stick manual transfer case, front manual locking hubs, or an EcoCrawler reduction unit that you can shift separately from the transfer case, into a low gearing range.

Now, for what this post is really about:

Spoofing the ADD electrically (@5678ta )

https://www.tacomaworld.com/threads/tacoma-add-delete-wiring-figured-out.464595/


This write-up is what helped me figure out how to spoof our ADD. It pertains to a 2nd gen, but the wiring itself is the same on both vehicles, functionally speaking. The colors are slightly different.

See comparison of wiring diagrams:

2nd Gen (ignore the yellow circle)



3rd Gen:



How the ADD works

When going from 2WD to 4H, the 4WD ECU energizes a spinning motor which spins until the limit switches have reached where they need to in order to confirm the switch, and cut the motor off. Once the ADD fork has successfully reached its “4WD” position, an indicator is provided to the ECU. The ECU will not light the light on the dash until both the transfer case and ADD confirm their actuators are in 4WD mode. At that point, the ECU sends an indicator to the combination meter (instrument cluster) over CANBUS.

Resistor needed?

It was previously thought that on 3rd gens, the 4WD ECU monitors the amperage draw on the actuator motor circuits to ensure the motors are present and functioning. The ADD actuator motor is powered/grounded by the circuits DM1/DM2 in pins 1 and 2 of the ADD connector, and pins 2 and 6 of the F12 connector at the 4WD ECU. As such, it was thought that a resistor is needed on these circuits to keep the computer happy when the motor is no longer present after being deleted.

In my testing, I have tested extensively with the circuits simply disconnected and no resistor in place for the ADD motor. I have shifted mine many times back and forth with no issues whatsoever. So at this time, I will say a resistor for the ADD spoof is not necessary. I could certainly be proven wrong. The 4WD ECU changed for the 2020 model year to accomodate the lack of a front diff temp sensor. Maybe they changed the logic or something too.

The testing that found a resistor was necessary was performed on a 2017, back during the development time of the 2WD Low kit. YMMV. If I hear otherwise that resistors are necessary on some models, I will update my post with that information. For me, the lack of a resistor means less clutter I install with my harness, and so going without is certainly better to me.


So now, we can focus on spoofing the ADD following the diagram from the post linked above, but modifying for the 3rd gen wire colors as I also posted above:


1 - DM1 - Red - Power/ground for ADD motor
2 - DM2 - Sky Blue - Power/ground for ADD motor
3 - ADD - Light Blue - Confirms ADD engagement
4 - GND - White/Black - Ground
5 - DL2 - Pink - Power cut for ADD motor (limit switch)
6 - DL1 - Light Green - ADD disengaged confirmation (limit switch)


So, need a relay to manipulate pins 3, 5, 6 of the ADD circuitry in order to spoof the ADD - see relay info below:

Thanks @caribe makaira for drawing this!


Relay:

86 - Ign 12V - pin 4 at F12
85 - 4WD Select - pin 13 at F13
30 - Ground - pin 10 at F12
87A - DL1 - pin
87 - DL2 & ADD - pins 2 & 7 at F13 - splice together and then connect to relay


That's it! The way this is set up, is that when you turn the 4WD knob from 2WD to 4H, the knob will ground the relay, switching it from normally closed (87A connected to 30) to normally open (87 connected to 30). This is all the computer needs to see in order to think the ADD is in place and operating normally. Nothing happens going from 4H to 4L, because the ADD is already energized. When you finally go back to 2WD using the knob, the relay switches back and the 4WD ECU sees the feedback from the relay and is satisfied.

Install photos (I'll add more when I remove the harness this weekend for additional testing):

 

Reserved for mechanical ADD delete

 

Reserved for transfer case electrical spoof

 

How about now?

 

I’ll add it to the post.

 

Mating for F12

 

Thank you for putting this together. By some chance will you be able to update this thread with any updated information about the t-case spoof as well?

 

I can. The thread didn’t get very much traction and so I kind of gave up posting on it. It’s a lot to type.

 

I would be happy to help if there is anything I can do, just let me know, thank you. Spoofing the ADD and T-case is exactly what I need, otherwise I am pulling the 4WD CPU and I am running a new standalone wire harness to the rear Toyota elocker and not using the 4WD traction control and crawl options. I can tell you that your work is at least helpful to me.

 

Well, I’m glad it can help someone. I’ve seen too many people have no solutions besides keep the actuators and zip tie them away so they keep “working” to fool the computer.

FYI, simply unplugging the 4wd ECU will throw all sorts of warning lights up on the dash. Very annoying and not really a good long term solution. You’ll want to keep the ECU and either fool it with my wiring info, or keep the actuators plugged in and zip tied so they can fool it. Either way you pretty much need to keep the ECU.

What I will probably do is send you a PM with the info. I still don’t really have what I want here typed up. I typed up pretty much all of the relevant ADD/tcase info for someone else in a PM, so I can likely just give you what I gave him. You mainly need to buy a 2lo harness, wire up 6 relays to it, and then since you need some inputs from the t-case to actuate those relays, you need to redo some of the t-case connector wiring so that you can repurpose some of those wires for carrying your new manual tcase switch signals into the cab.

 

OK, again, I would be happy to help type stuff up here and do basic drawings as well. Right now I have installed a 4runner t-case, trail gear crawl box into the truck with the 12th State ADD wire harness. All of this is working. I also wired up the 4runner t-case 4WD and 4Lo indicator switch wires to the t-case wires 9,10, and 12. The rest of the wires are just wrapped up at the moment. I do have lights, but they are just ABS/Traction Control lights which I believe you can clear given this post: https://www.tacomaworld.com/threads...sfer-case-install.693450/page-3#post-28239675.

 

I used a 12 pin connector just in case I wanted to throw the automatic back in for any reason.

 

Just sent you a long PM with all the details I sent the other guy. Spent 10 or so minutes correcting some it because I have some updated information since I talked to him.

The jumper harness I reference - looks like you sorta have already dealt with that. As long as you now have the ground signals from the 4WD and L4 switches on the t-case available in the cab, you can use them to splice to your custom harness with all the relays to keep everything happy.

Looks like you’re making some fine progress. I’d love to do the manual case, I just don’t know if I’m bothered enough to actually do it.

 

Here is what my shifters look like in the cab. I purposefully put them in the e-brake location. I didn't want to chop my console up and the e-brake was removed when a did a rear brake disc swap.

 

Here is what they look like under the console. It was a bit of work designing them around the auto-tranny shifter plastic housing and getting them to the e-brake location.

 

What they look like with the auto-tranny plastic housing in place.

 

Hypertech has the harness that mates the 4wd Control ECU:



The C9 to the Combination Meter is same connector to 4WD Control ECU.

 

Thank you, by some chance do you know the part number?