Ducky

My truck is in the garage (Yes it fit) drying off...

aowRS

SWEET!

Is the dash apart yet????

Andreas

Coda99

Had my truck in the garage for a good part of the afternoon. Located the VSC ECU did quite a bit of tinkering. There is no wire on the VSC ECU harness for the TRAC OFF SW (pin #C26). With only 2 wires (on the 2-wheel drive harness) it seems the computer only needs a momentary ground the toggle the TRAC on and off. I'm not brave enough to short the pin on my truck yet. I did verify my previous suggestion of opening the ingnition wire (#D7). The same as pulling the fuse. It did shut everything down and reset all when power was restored without have to turn the truck off and back on. So far all I can think of is to connect a latching relay to the factory switch and open the ignition wire.
Hope someone can come up with a better solution. Or wants to try and short pin# C26.
Later

LEADfoot

hey there...fiirst post..sick of vsc too VERY sick of it

got anm '03 and i love the rig...you all know the rest

i might be missing the point here but
it looks like TRAC-control is run by the ecu when...in part...
the right info is processed by the VSC computer via all outboard sensors

the manual states (and it is NOT gospile) that using the VSC/TRAC-off
button only works up to a set mph... then it turns back automaticly

we may never be able to completely get rid of the throttle-back feature
unless someone can hack the ecu

i did the "AndyMod" and on dry pavement and the throttle seamed "confused"
and wouldn't give as much power as normal unless i was half way through a doughnut...then it lurched and cut...which might have been the rear diff

so i think we need to
A) by-pass/hack the CENTER-LOCK switch to fool the ecu and VSC computer into thinking its in "LOCKED 4WD" turning itself off w/o noticing the speed of the vehicle and turning back on automaticly

B) turn off the yaw and wheel sensors so it doesn't see the vehicle slipping
and cut the throttle

sound good?...why am i talking like my esuvee is a person with reasoning capability anyway thanks

aowRS

Coda,
I like this thinking. What are your thoughts on how the actual TRAC OFF switch operates? My switch is sitting here on the desk begging to be integrated into the dashboard....

Ducky, you following this?

Andreas

Ducky

Well not so great news...

I have tried several configurations of the switch including some bawlsy "mebbie im reading the diagram wrong" choices... and still a no-go.. It will not disable (running, or just on ACC on key position).

why not labled as "Bad news"? because i didnt seem to smoke my ECU lol... so all in all its not so great lol.

aowRS

Ducky,
Do we know what the upper and lower pins of the switch do?

Andreas

Ducky

When hooked up to my DMM when pressed it shorts... just as we thought a momentary switch...

Ive got new problems though unrelated.. I just found out my Air locker in the back is leaking air in my diff... you can hear the air come out the breather...

aowRS

Coda,
Where exactly in the VSC ECU located? This TRAC OFF switch is quickly gathering dust on my desk....

Andreas

hillbilly

One of the ECU's (don't remember if its the 4WD or VSC) is located behind the drivers kick panel (by the drivers left foot). Remove the screws holding down the door trim and pop it off, then just pop the kick panel off.

lee

guys,

my roomate is an electrical engineer. is there anything specific you want him to look at?

aowRS

Lee,
Unless he's already done so, could you have him read through the entire thread and the links, and give you some thoughts on what we may be up against? There have been a ton of great suggestions so far, but no real-world clean answer. We do know that we can interrupt one or more of the wires at the pressure switch and shut the systems down (one wires appears to be a ground). But that probably means a restart of the truck to regain the sytems.

Have him review the wiring diagrams that have been posted and the wiring associated with the 2WD TRAC OFF switch aplication (also posted). Any input helps. I think most of us would like to do the minimal amount of cutting necessary to make the stock switch work. But at this point I am ready to cut/graft/solder/etc.

Andreas

hillbilly

Andreas-

Here's an image of the ECU locations:

aowRS

Thanks Hillbilly. Looks like a scan of the Space Shuttle's electrical setup...

Andreas

Coda99

Andreas,

Drop the panel below the steering wheel and look for a silver box the left of the brake pedal. 2 12mm bolts hold the unit in place. One on the top and one on the firewall. The VSC ECU is marked with stickers (can't miss it). Looking at the parts location diagram I don't know where and what V16,17,18,19 are. Unless that is for the 2-wheel drive model. Each plug is marked with numbers on the sides next to the end wires. With these numbers each wire and pin number can be located. Just follow the colors and numbers on the diagram to figure out which plug is which. I still have to order my switch and find some relays. It might be a while before I get time and can get under the dash again, but will keep you posted if I find something new.
Good luck!
later

aowRS

Coda,
Thanks. Check a few pages back to two sources I posted for the TRAC switch. THe price was right and I had the switch in a few days.

Andreas

calamaridog

It's important to note the Space Shuttle has less computer power than the new 4Runner.

aowRS

I'm reposting the link to the '01 schematics, as a few new people have joined the thread. Hopefully this helps to shed some more light.

Schematics

Andreas

Pat2002SE

I have been following this post for a while now and keep hoping for a "fix" so I can switch off the VSC/TRAC. I have pulled the 3 wires at the master cylinder and it is awesome to have the power back. I have emailed the Toyota website that has been discussed in the post here with my complaints. Please keep trying guys! I appreciate your hard work.

aowRS

I decided to waste part of my morning and go back through the responses to extract all of the suggestions and potential solutions. I hope this helps to get the thread back on track and to show all of the thinking that has already occured. I think a solution is on the horizon!


"find out how the trac is being triggered (i.e. wheel spin, abs sensor maybe?) and then make a hardline switch so you can cut the connection when you want.
if the cpu doesn't detect wheelspin then the trac shouldn't engage. ofcourse this ultimately means abs will be disabled. then again how about just removing the abs relay then it won't detect slippage?"
- GoodTimes

"I unplugged a sensor on the brake master cylinder. This disabled the VSC and traction control but the ABS functions normally. On the Sequoia it was the sensor farthest forward and on the bottom of the master cylinder. If I was to wire in a toggle switch to one of the wires at the sensor I could select off or on."
- Manson (4X4Wire)

"What about wiring in a simple 12v ice cube relay, with the ABS on the normally opened contact and the switch for the VBS wired to the coil of the relay , Then when you turn the VBS off the ABS turns off as well. The ice cube relay would be powering a closed loop when the VBS is on and open loop when off. The relay has 2 sets of open and closed contacts so there are more options. Does this answer the question??"
- Dublin

"I was able to reduce the effects of Active TRAC removing the relay mentioned in the above post, but never completely able to defeat it. The ABS system seems to have redundant electrical paths, which allows the ABS system to remain functional in the event of a single component failure."
- Hillbilly

"With the work I've done, I believe disabling the wheel spin sensors may be the best/simplest, if not the only, route since the ABS controller appears to have multiple electrical paths for safety reasons."
- Hillbilly

"Fookers! Give us a switch frigging aholes lol..."
- Ducky

"So, why not find the wire, or switch that disables the VSC/Trac when you select into 4LOW, and make a jumper switch @ that point. So with a flip of a switch you are fooling the trac/vsc or whatever it is that you are fooling to think that the t-case is in 4LOW. But, you are actually in 4HI with the light on the dash again."
- Mark Fit

"In theory, interupting the ABS wiring with a switch would take care of everything - as both TRAC and VSC rely on the ABS system."
- aowRS

"I have a 2001 Taco, so no TRAC. However, the ABS actuator ECU (co-located with the actuator) gets a signal from the 4WD Low switch (same one tapped into for the "grey wire mod" that fools the E-locker into locking in 2 or 4 wheel high). I don't have ABS, but I'll bet the signal is designed to cut off ABS when an ABS-equipped Taco is in 4WL.
According to the FSM, the switch (on a 2001 Taco) sends a ground signal (all down grey wires) to terminal 18 on the 4WD ECU, terminal 19 of the ECM, terminal 14 of the ABS Actuator/ECU, and to terminal 8 on the E-locker ECU.
I don't have the electrical wiring diagram manual for a vehicle with TRAC, but based on previous posts, I'll bet the same (or a parallel) circuit is used to cut off the TRAC when the center dif is locked."
- Whizkidder

"here is what i believe to be the pinouts for the normally open “trac off switch.” please verify before hacking at your own risk. i have not tried this “yet” as i do not know what would happen in the ecu logic if activated. that ecu box might be a little expensive if it starts smokin’.

http://community.webshots.com/album/254318478jhyxPZ

“trac_sw_pic1” pic is pin 26 on connector C on ecu. note there is no blue wire (L=BLUE) in position 26. it would be nice if someone w/ a 2wd model w/ trac switch could verify the blue wire for that position.
“trac_sw_pic2” is pin14 (W-B = white w/ balck stripe) on junction block 3 connector 3E located by steering column. there seems to be an additional bank of two connectors on this junction block on the bottom that is not in my 2001 manual or the 2002 manual referenced below."
- mikNtx

"the more and more i looked at the schematics over the weekend, it seemed the switch is just a connection to ground and pin C26 of the ecu."
- mikNtx

"a. I believe the same part number ECU is used for both the 4WD and 2WD (which has the TRAC OFF switch.)
b. I believe the ECU has software/firmware inside it. If Toyota does configuration management like we do where I work, if a piece of hardware (ECU) has software/firmware in it, different versions of firmware result in different part numbers. In this case, 2WD or 4WD would have a different part number.
c. Given this, since the part numbers are the same, my thought was that the firmware for the VSC/TRAC ECU is the same, and that the addition of a switch would take effectively turn the "TRAC" off as it would on the 2WD.
I would be nice if someone were to check what I said above, and if they agree, try to ground V18, pin 26 and see what their results are. Also, if my belief is true that different firmware has a different part number for the ECU, the it is possible that there is another pin that the ECU reads to tell it that it is a 4WD ECU rather than a 2WD ECU."
- emplusten

"If you look on page 158 of the 2002 electrical manual which describes the 4WD, you'll see that pin 20 of F7 (4WD ECU) goes to the 4wd lamp. If this line is also the sensor to say "I'm a 4wd ECU" to the V18 VSC ECU on pin 24, then the experiment I tried when I was in 4WD may work if you put the truck in 2WD. We'll have to give that a shot."
- emplusten

"A knowledgeable and rogue Toyota technician that's willing to part with the knowledge sure would be handy."
- yabedude

"I checked my factory service manual again this morning and decided to unplug the "Oil Pressure Sensor Connector" at the master cylinder. This is the forward facing of the various plugs (see pic below - sorry for the huge size). What I found is that the "VSC OFF", VSC TRAC", and "ABS" indicators are then illuminated. More importantly, I could sling slushy snow all over the neighboring county. 2WD, 4WD - didn't matter."
- aowRS

"it appears "E2" is a ground as different voltages are measured off it and "VCM" and "PMC"."
- mikNtx

"anyway, as an interrupt for the master cyl pressure sensor, i would lean towards what appears as a ground "E2" or the signal + "PMC". "VCM" is a constant voltage (4.7-5.3V) with IGN ON."
- mikNtx

"i tried it in 2wd only. it acted as if it did nothing different. i got the familiar de-throttling and the skid indicator to light up. also checked my pin 26 switch connection several times as that connector is pretty deep. seperately, i'm also wondering if ABS is disabled in the 2wd model when their TRAC switch is activated (similar ecu theory).
- pin 24 -
if you have the diagnostic manual (vol1), check out both circuits on p. di-331 and di-347 on the vsc / center diff locking circuit. its interesting as i think these circuits are key in getting the thing to behave the way we want it. they both include the V18 pin 24 (CD).
for kicks, i decided to pull the master cyl sensor and it seemed to work as described earlier. on my 4r, the abs, vsc off, & vsctrac warning lights stayed ON even while plugging it back in (engine running). they went off and performed normally when i restarted the truck. i'll try it again over the weekend. from the manual, pulling the master cyl sensor fails the system in a higher level (ABS) failure mode (ref di-226) vs the VSC failure modes p. di-228. i'm also wondering if failing one of these circuits will get me the "VSC OFF" only fail safe mode. i would only like to see one failure indicator vs three."
- mikNtx

"About automatically reinstating TRAC functionality when the engine is cut ... a relay, or several, would seem to be the way to go. A simple push button that acts as a toggle (on or off) to a relay that is wired such that when the ignition is disabled, the relay tosses the latch(s) to enable TRAC again."
- yabedude

"anyway, from “p3” diagnostic page, it appears PMC’s voltage varies as the pressure changes. disconnecting it should fail the ecu as it will output zero voltage. as someone suggested earlier, the use of bridging each circuit w/ alligator clips and shutting them down independently is the least invasive method to prove it works."
- mikNtx

"you need to try having two connections at a time and disable one, if there is a ground in there then having only one connection won't do anything like you found out.
I would disconnect only the VCM line and leave the other two on."
- TacomaTRD

"Everyone is trying to correct or adjust the output of this module. Let's look at the input side. What if we kill the ignition to this module and not let it turn on. My guess is that pin# 7 (labled IG1) might be the ignition wire. If this works it may correct the problem of having to restart the vehicle to reset the ABS, VSC, and TRAC."
- Coda99

"Located the VSC ECU did quite a bit of tinkering. There is no wire on the VSC ECU harness for the TRAC OFF SW (pin #C26). With only 2 wires (on the 2-wheel drive harness) it seems the computer only needs a momentary ground the toggle the TRAC on and off. I'm not brave enough to short the pin on my truck yet. I did verify my previous suggestion of opening the ingnition wire (#D7). The same as pulling the fuse. It did shut everything down and reset all when power was restored without have to turn the truck off and back on. So far all I can think of is to connect a latching relay to the factory switch and open the ignition wire."
- Coda99


Hope this was helpful.

Andreas