Rear Diff Lock Anytime Mod 3rd Gen DEVELOPMENT

Which is great to hear. I was going to just do that with discrete off the shelf components, but much better an integrated solution. This just leaves us one great question that I don't know the answer to, or how to get the answer.

Do we need to disable ABS and TRAC when we enable? Does anybody know why toyota disables it? Did 2nd gen disabe?

 

I don't think we will need to, I haven't tried it though. I'm assuming since both left and right rear wheel speed sensors will report equal speeds when the diff is locked, there wont be any errors/flags thrown. The ECU will think its just driving fine down the highway.

 

I agree in theory, but why does Toyota do it. Not for fun I assume. In my opinion, When engineers put in a function like that, some failure mode is being considered....

 

I agree with your failure mode point...everything is for a reason. However, I think the ABS and VSC disable is just because they are assuming by the time you are engaging the locker, you are stuck and off the roadway anyways. It also is linking 3 of the wheels (4LO and locker means 3 wheels going the same speed), and the need for ABS and VSC is nil.

 

After thinking about it again, we may need to disable ABS and TRAC. The car may detect slippage of the front wheels and try to correct for it by applying brake pressure on all/some of the 4 wheels of the car. By disabling TRAC, the car won't correct for the slippage.

 

The ABS and VSC disable is easy enough though, you just break the circuit/fuse if I remember correctly. I think there is a wire going to the ABS pump that you can just break/ground out and it makes the truck think it is inactive. Maybe a wire coming from 4WD ECU...........don't have the EWD to check.

 

So I think, for the moment we need to assume that we need to disable these. I actually don't see an easy way yet. I will upload the wiring diagrams I have tonight.

 

Trac uses abs to regulate wheel speed for optimum traction. Couldn't you just hold down the vsc button to turn off Trac then actuate the locker? Not to mention you can is the locker and multi terrain select together. That also utilizes abs. No need to deactivate those in my opinion.

 

Somehow the locker needs to be removed from the 4wd ECU so it works like an aftermarket locker would. I'm just not smart enough to do it.

 

Agreed.

 

This thread has the Wiring Diagrams for 3rd gen I believe
https://www.tacomaworld.com/threads/wire-color-code-drivers-side-kick-panel.495772/#post-15355275

 

I will try and see about locking it. Disconnect harness and see if it unlocks. Also will try the engage locker and turn off truck and see if it unlocks.

 

If I had an off road it would be on the jack stands buddy.

I can see a reason to deactivate engine trac control. But I see no reason to worry about abs or brake activated traction control. I don’t think vsc will activate with both rear tires spinning at the same speed.

 

Please do.
See how pissed the computer gets when disconnected too, when changing gear modes 2hi, 4hi, 4lo, engine start, etc.

It may well throw some codes at you, but reconnecting everything and power cycling the engine will almost certainly reset it.

Let us know. Thanks.

 

You mentioned PWM. Could you use a switch like this for testing or simulation of the factory signal?

I think the voltage might be too high also.

 

I did the old gray wire mod to lock the rear in 2wd in my FJ. It disabled all nannies including ABS as it should. You want TCS, Stability, ABS, etc disabled if you're enabling the locker in 2wd.

 

Yes, I think it could. @gman36 I believe said he was working on a single circuit solution.
I will keep working on several off-the-shelf commercial components linked together, but it will be bulky and won't be nearly as elegant as a on-design component.
Furthermore, when it comes to efficient electrical design, that is NOT me. I haven't started designing any circuits, not until we try and answer all the fundamental questions. I have a few results to discuss from this weekend.

 

I locked the rear diff, shut off truck, and it blinked that it was unlocking

Once I drove forward it came unlocked

 

Current Data Review Summary (my best beliefs up to 3/12/18):

• Brief attempts were made to confuse the ECU to think it was 2wd-Locked configuration, (like a prerunner), to allow locker to operate without being in 4Lo. This was ineffective. Looking at the wiring diagrams, and the work on 2Wheel Low, makes me assume that a simple 1 wire mod to confuse the ECU will not work.
• The rear locker does not operate internally like the previous gen. (Previous gen had a worm drive motor to operate a fork entering into the diff to lock it. It included position feedback wipers that were used to control the motor. When locked the motor stops running. The 3rd gen uses an electric magnetic puck inside the diff to operate the lock from within the diff. From the repair manual it looks very similar to Eaton type electric lockers.)
• Diff lock circuit in 3rd gen consists of a pair of wires of to the diff lock, a grounded lock/unlock signal feedback wire, and a grounded momentary lock switch.
• The 3rd gen diff lock coil current must be maintained to keep the diff locked. Diff coil reads approximately 3 ohms in free condition. ECU is programmed to apply approximately 3.7 amps when feedback shows unlocked, and 2.0 amps when feedback shows locked. This appears controlled by a PWM circuit in the ECU. We don't know if we need to do this as well or if a constant 3.7 amp current will overheat the coil?
• I believe that we need to make sure to disable ABS, VSC, etc when anytime lock is active, although I cannot be positive why we need to. I do not believe Toyota did it by factory that way for fun, but I can't prove without a doubt. If lock coil circuit is open on startup, ABS and VSC are disabled. This check appears to ONLY occur on engine startup unfortunately, as this would be ideal to use.

So, now NEW DATA from this weekend.
Finding a way to disable ABS and VSC does NOT appear simple. It looks like disconnecting power to the ECU is the most likely effective way, however with the interconnections of ABS, Hydraulic Brakes, VSC, and 4WD its not simple. I tried 8 power circuits to see what was most effective without undesirable impacts.

My best recommendation at this time is Disconnecting ECU-IG No 3 power wire (Pin 46 to Skid Control ECU Master Relay Connector S1) appears to disable ABS, VSC, and Crawl Control, as well as 4WD MODE CHANGES.

If anybody can actually determine a specific testable better way to disable ABS, VSC please present it.

Over the next day or two I will start working on a suggested Rev0 schematic, that we can start throwing rocks at. At this time, I intend to suggest a separate switch for the anytime override locker (and keep the blueprint switch as-is), with its own set of lights. Alternatively we would need to see if the truck is in 4Lo, and either operate the normal circuit or the new circuit.

 

Thanks
all matches, seems that we are understanding it consistently.