Locker mod?

[Comattack]

Originally Posted by tacosupreme

That didn't work either. The computer won't let you shift out of 4LO with the locker unplugged. The warning lights all go haywire, but no buzzer for me, I have removed all THREE of them. Have to tell the computer it is disengaged even though it isn't. This may be overcomplicated, but I think this is the ticket, the computer knows 4LO is engaged from
A) The switch position on the dash
B) The L4 indicator switch (wherever that is)
C) The transfer case
D) The ADD (front end) must also be engaged before the locker will lock

So if I trace down where those four wires go and how to send a false signal through them, bingo. Can you guys think of any other signal that changes in 4LO?

Which wires did you unplug?

The limit switch might be the tricky one because it sends either an "unlocked" signal OR a "locked" signal to the ECU. It's always one or the other, so simply disconnecting it might make the ECU think "WHERE THE HECK DID THAT LOCKER GO?" And it goes haywire. You'll probably have to ground the wire that tells it it's unlocked in addition to disconnecting the actuator and indicator switch.

Wait! I just thought of something... The OEM locker switch is still on! Telling the computer it's supposed to be engaged! That's probably ANOTHER reason why it won't switch out of 4LO!

DOH!! Round in circles we go!

I think we're going to have to do some really complicated wiring to disconnect the actuator, limit switch, indicator switch, AND the OEM button, while still leaving an "unlocked" signal from the limit switch. Your talking a few relays and a real rats nest of wiring in there.

I had a solution for all that "miscommunication" in order to add a second computer, but then were still talking about bypassing the ECU and safety features completly and/or engaging it manually.



Hate to say "I told you so." (ok, no I don't)

Signed,
~"Negative (but right) Nancy"

[Comattack]

I on average have between 5-8 hours A DAY at work that I have to kill somehow. It's a rare occasion that I actually have things to keep me busy (gotta love Uncle Sam), so I have passed the time looking at these schematics, reading the manual, and understanding how the thing works for DAYS at a time!! If there is a way, I can tell you how to do it! (already figured out a couple.)

Tell ya what I'll do, SINCE I'M SUCH A NICE GUY!
You tell me how you want to wire it, what you want to bypass... whatever sensor or control you want and I'll tell you how to do it! How's that sound?!?

[tacosupreme]

All of the wires from the aforementioned locations all end up in one place, Connector F-13 on the 4wd ecu. Pin 15 goes from +12VDC to -12VDC as soon as low range is selected, same with pin 17, pin 13, pins 23 and 24. Seeing a theme? How much of a "rat's nest" would it be to tap into those wires with a grounded switch? Or, at least in my case, find out where those ground signals feed into on the circuit card and solder on a jumper there. If I get it to work I could even order a female and male connector and just make a "plug and play" mod to make it easy for everyone.

[QuasiInsomniac]

I've liked Plug n' Pray ever since Windows 95.

[Comattack]

Originally Posted by tacosupreme

All of the wires from the aforementioned locations all end up in one place, Connector F-13 on the 4wd ecu. Pin 15 goes from +12VDC to -12VDC as soon as low range is selected, same with pin 17, pin 13, pins 23 and 24. Seeing a theme? How much of a "rat's nest" would it be to tap into those wires with a grounded switch? Or, at least in my case, find out where those ground signals feed into on the circuit card and solder on a jumper there. If I get it to work I could even order a female and male connector and just make a "plug and play" mod to make it easy for everyone.

All of this lines go from +12VDC to -12VDC because they are all grounded WHEN the transfer case IS in 4LO. IF your were to somehow ground all those wires, you'd have difficulty switching to 2HI or 2LO because the computer would read it being stuck in in 4LO. (but still continuously trying to move all the mechanical parts)

Pin 15 is grounded because that is the 4WD control switch (the one on your dash). It's just a signal to tell the computer what gear to shift to. 4WD control need the CORRECT signal, not a fake one or it won't shift right.
Pin 17 is he indicator switch for 4LO. (will screw with the 4WD computer if it's actually in another gear)
Pin 13 is the limit switch that disengages the actuator assembly when it succesfully shifts to 4LO (keep it permanently gounded when you switch to another gear, or by using a switch, and the actuator motor won't disengage until that ground is removed)
Pin 23 & 24 are readings from the ACTUAL transfer case. In any mode OTHER than 4LO only ONE needs to be grounded at a time, or the computer will think it is shifting improperly.

If you really want to mess with that 4LO signal, I'll tell you how in my next post.

[Comattack]

Originally Posted by tacosupreme

All of the wires from the aforementioned locations all end up in one place, Connector F-13 on the 4wd ecu. Pin 15 goes from +12VDC to -12VDC as soon as low range is selected, same with pin 17, pin 13, pins 23 and 24. Seeing a theme? How much of a "rat's nest" would it be to tap into those wires with a grounded switch? Or, at least in my case, find out where those ground signals feed into on the circuit card and solder on a jumper there. If I get it to work I could even order a female and male connector and just make a "plug and play" mod to make it easy for everyone.

All I'm saying is the 04 and earlier tacomas has a separate unit for 4WD control and for the Rear-Differential lock control. 2 Computers! Except for ONE wire, they are completely isolated from each other. That is the one wire you ground in the "grey wire mod". You are ONLY tricking the rear differential computer into thinking it is in 4LO. The actual 4WD computer still reads the correct sensor readings to deterimine what gear it is in for proper shifting & engagement. That is how it works on an '04 or earlier. (keep that in mind when trying to trick the '05 computer that conrlos BOTH with only ONE signal.)

An '05 Prerunner computer works almost exactly the same as the '04 rear differential computer, only it has no 4WD control portion (neither built in, nor an external computer). That's why it engages in 2HI.

The '05 4X4 computer we have been talking about has both computers integrated into ONE. There is NOT a separate control unit. That is the problem. You need to send a ground signal to the Rear differential lock portion of the computer ONLY, but you still need the SAME signal for the 4WD control. And there are several different sensors that provide feedback to the computer to do so. That is why you cannot simply ground a wire or fake a signal to the 4WD ECU to get the rear differential lock to work. You will have to try and fake ONLY the rear differential lock portion of the circuit board, but NOT the 4WD control portion of the circuit board. (but they both read from the same signal). That's an internal computer wiring issue. Forget trying to trick the computer with a false signal with the external wiring. The 4WD potion of the computer still needs that signal.

What signals does the 4WD computer need to shift properly? You need pin numbers? Ok, how about ALL of them except for pins 1, 2, 13, 16, 20, & 21 of plug F12(A). Those are for the differential lock. The 4WD needs the signals from all the other wires to work properly. Your problem with the little test you did was that pin 16 (plug F12) from the OEM switch was still engaged when you disconnected everything.

Make sense? Basically In order to do all THAT, without adding other components (another computer or independent actuator control), you would have to map the circuit board, isolate the rear differential control from the 4WD control, and ground the proper circuit (rear-diff) after you isolate it from the 4WD. Not an easy endeavor, but maybe as a chip repair guy you can handle it. (just follow pin 17 yel/blk wire on plug F13(B) to the circuit board & see where it goes) This is not a try, try again job though. Once you screw up the circuit board your f'd! (tacosupreme may be able to repair his... that's what he does. Your typical DIY'r cannot)




Engaging the lock and then tricking all the sensors to make it think it is unlocked and them switching out of 4LO, actually isn't that bad of an idea. You just have to do a little more than expected. (If you don't cut the ground to the wire in the right spot, the ABS might re-engage as well, since your pulling that signal from the computer to make it think it's unlocked).

Here's what you need:
At the flip of a switch, you need to disengage:
-The (rear diff) indicator switch
-The limit switch wire for the engaged posistion,
-But Re-Engage the limit switch for the "disengaged" position
-Also need to disengage the power lead from the OEM locker switch to the 4WD computer
-If you do all that, you MIGHT be able to leave the actuator alone, but since your doing all that, I would also disengage that, just in case.

You need all this to be done SIMULTANEOUSLY so the computer doesn't go haywire and/or the locker doesn't try to disengage. IF this works successfully, you may still have to switch BACK to 4LO in order to disengage it. Not positive, but it's possible if you have it in 2HI or 4HI and the computer suddently senses the locker is engaged, then it might go haywire again.

Test it again, except this time, remove the key from the ignition... disconnect the wires and disengage the locker switch. (this just simulates EVERYTHING being disconnected simultaneously until the power is turned back on). Then turn it back on and switch to 2HI or 4HI. If it works, turn off the ignition (leave it in 2HI or 4HI), plug in all the wires and re-engage the locker switch, and see if it causes some trouble (Which will verify the validity of my re-enagement theory... if it really has to be done in 4LO).

If it all works, I can work up a basic wiring diagram later just to show you what all is involved in the rewiring. You'll possibly need a switch with the ability to interupt power on 3 different lines (6-pole) and probably one relay (at the LEAST). If that switch is not available you may need as many as 4 relays. (that's where that "rats nest" comes in)

Try it and tell me what you think!

[QuasiInsomniac]

Very very well thought out. Thanks for the post(s). I think I might try to disengage the locker tomorrow and see if it freaks out.

[Comattack]

So how are things coming on that locker? Tested anything else out yet?

Just out of curiosity, what happens when you disconnect EVERYTHING for the locker (already disengaged of course)? I'm working on another solution and just curious what the 4WD computer does with all the locker stuff completly diconected.



Right now, I'm checking on a source for a pre-05 diff lock computer for my other idea. So we'll have a second computer to control the diff-lock inderpendently. It'd require about the same technical skills as to wire in a switch or something, so I'm assuming cost is the only objection you guys have with wiring another computer...? If the price is reasonable, I'll draw up a diagram and pass along on the needed info.

[tacosupreme]

I e-mailed Aisin electronics inc in an attempt to get circuit card schematics. I have been on the road for a week and haven't had time to mess with the mod, too busy playing in the snow and I think I am burnt out on it for a while. I'd call aisin direct, but I'm overseas. Maybe you could give it a shot
209-983-4988. Maybe try to pose as a stealership mechanic or something official sounding and see if you can get any schematic info, you have the part numbers right?

[Comattack]

Originally Posted by Comattack

So how are things coming on that locker? Tested anything else out yet?

Just out of curiosity, what happens when you disconnect EVERYTHING for the locker (already disengaged of course)? I'm working on another solution and just curious what the 4WD computer does with all the locker stuff completly diconected.



Right now, I'm checking on a source for a pre-05 diff lock computer for my other idea. So we'll have a second computer to control the diff-lock inderpendently. It'd require about the same technical skills as to wire in a switch or something, so I'm assuming cost is the only objection you guys have with wiring another computer...? If the price is reasonable, I'll draw up a diagram and pass along on the needed info.

Got a quote for the '04 Diff-lock ECU. (used)

$100 + S&H if you want to wire it up and bypass the factory 4WD computer.
Everything will work exactly the same as it does now, except in 2HI & 4HI as well.

This is what I'll be doing to mine. If other people are interested, I'll post a link after I order mine (for all my hard work, got to make sure they don't run out and I get mine too).

Working on a wiring schematic as we speak!

[Comattack]

My schematic is finished if your interested, but I decided not to post it until I get to try it myself. I don't want to be responsible for any problems with your vehicle.

PM or email me if you want a look, however any experimentation will be at your own risk.

[Comattack]

.....

[tbrown78]

Why don't you just wait until you have a truck of your own? Is it that imperative that you have everything figured out right now? I'm sure you have some good ideas but tacosupreme seems like a pretty smart guy and he has actual hands on tinker time and has been playing around with this for a while. Calling him out in the public forum and whining about not getting credit for your ideas after he was sending you PM's on his thoughts and personal experiences is wrong dude. Do like he said, wait until you get your own truck, if you figure something out you'll get all the credit in the world. OK.

[tacosupreme]

"I can almost GUARANTEE I would have a solution."
Yeah almost. Almost only counts in horseshoes and handgrenades.
The fact is that neither you, nor I has come up with anything that has actually been proven to work better than Dick Foster's idea of just wiring up a seperate circuit for the damn thing, and unless you have access to some information I don't have, you have absolutely no idea what parameters the IC chips operate on. Yes computers are simple little devices that think in simple little one's and zero's, and probing away with test equipment hasn't resulted in a solid map of the complete circuit. Regaurdless of how many hours you have spent staring at the PDF's you can't substitute holding a real 4WD computer in your hand with test probes hanging off of it. It's like getting laid, you can imagine what it's like by staring at a computer screen, but it's nowhere near as good as the real thing.

[Comattack]

Understood...

Yeah, I'll wait till I get my truck... just thought I could help. And knowing that it was already completed successfully would be a big plus when I get mine. (Not that I have any problems being the pioneer.)



**************************************************
I'll post this and leave it alone until I get mine.



Here's my reasoning for why I believe a second computer will work (and still disable ABS), and not make the 4WD computer go haywire with the locker components disconnected.

The Sport Model (4X4) still has the same computer except without a locker, so we should be able to disconnect the locker and simulate all the neccesary signals to make it think the locker does not exist, just the same as the Sport 4WD ECU. Make sense? If we can remove all the locker components from the computer successfully then we can wire them to a second computer.

ONLY VSC is disabled on a 4X4 when in L4 (ABS is still active).
A prerrunner has no L4 signal to disable VSC with the Locker engaged (look at the ABS w/ VSC diagram and you'll see that wire is only connected to ANYTHING on a 4X4), so the ABS indicator (from the diff lock indicator switch) should be sufficient to disable ABS as well as VSC, just as a prerunner would. This circuit is maintained by moving the wire from the old computer to the new one.


There are 4 items of concern regarding the locker. 1) The On/Off Switch, 2) The limit switch, 3) the indicator switch, and 4) the actuator (motor). In order to engage the locker in 2HI & 4HI, we need to make the 4WD computer "think" it is permanently disengaged, but still engage the locker and send signals to the ECU to disable ABS & VSC. Correct?

In the disengaged position, here's where were at:

1. On/Off switch has no continuity (no power or signal to 4WD computer). Therefore, Can be disconnected without tripping computer errors.
   
2. The limit switch: Terminal 13 (RLY1, Plug F12) is grounded, sending a disengaged signal to the computer. Terminal 21 (RLY2, plug F12) is open. #21 can be disconnected. If disconnecting #13 causes an error (in the off position of course) then that wire can be grounded to maintain that signal.
   
3. The indicator switch: Termnal 20 (RLP, Plug F12) of the 4WD ECU sends an on/off signal to the dash light causing it to blink until the indicator switch is grounded, which causes it to light up solid. The Junction box on that wire in the diagram, also splits off to the Skid ECU, a separate connection than the L4 connector, to disable ABS. You have to look at the ABS diagram to find it. Terminal 26, Plug S1 on the Skid Control ECU w/ VSC; Terminal 7, Plug S1 on the Skid Control ECU w/o VSC (2 different control ECUs). When the indicator switch is grounded, it ALSO grounds the terminal for the Skid ECU therby disabling ABS. The indicator switch wire is an open circuit otherwise (only blinks when enaging, we want it to think it's permanently disengaged), and should be able to be disconnected without a problem and attached to new computer (which would control the same functions).
   
4. The Actuator (motor): Obviously we would diconnect this and connect to the new computer. Shouldn't cause the 4WD ECU any problems. If disconnecting it alone in the off position trips the computer, than you can cut the wire at the ECU and simply insert a resister with the same ohm load as the motor. This would simulate it still being attached. (But I doubt it is neccesary).

That should cover all of our Differential Lock circuit with regard to the 4WD ECU.

I thought this out pretty well, however there may be something I missed. If there is, I am not aware of it. (but I admit there could be). There also could be something that I thought was obvious and therefore failed to mention. If you have a question or comment, feel free to speak. I'll answer any questions about my "idea", but I think I have contributed all I can. I can help with wiring problems/solutions, but reconfiguring a circuit board is not my expertise. (Hit up TacoSupreme for that one)

If I don't hear any comments/questions directed my way, I guess I'll just report my success in a couple months.


**************************************************


This info came from several different diagrams.

• The Prerunner 4WD computer for the diff lock (reardifferentiallock_2wd.pdf for 2005; reardifflock_2wd.pdf for 2006).
• The 4WD ECU for a 4X4 (multimode4wd_reardifferentiallock.pdf for 2005; multimode4wd_diflock.pdf for 2006),
• the ABS w/ VSC, Trac Etc (abs_trac_vsc_autolsd_dac_hac.pdf; both 2005 & 2006)
• the ABS w/o VSC (abs.pdf in the 2005 Diagram; abs_wo_vsc.pdf in 2006 diagram)
• Owners manual, Section 1-7 (17.pdf; both 2005 & 2006)

**************************************************


If you want to try to check my theory of disconnecting the locker (to prove or disprove), give this a try.

With locker disengaged:
Disconnect the on/off switch.
Disconnect the actuator (motor).
Disconnect the Indicator switch from the ECU. (pull the plug and carefully remove the pin or something)
Leave the Limit switch intact and connected to the ECU (this one is easy to creat a dummy signal in the off position, no point going to extra trouble to ground one wire)

If you get errors and/or buzzers it means one of two things.
1) we need to create a dummy signal for the motor as well
2) or I obviously I missed some detail somewhere.

No Errors/buzzers.
1) Ground wire for limit switch (everything now completely disconnected/disabled)
2) and you can follow the above idea to wire a second computer.