A-trac in 4lo on all 2016 4x4 Models Non Trd Offroad

L4 at startup: green drivetrain diagram light indicates 4wd
Press squiggly lines car button, nothing happens
Hold same button for a few seconds (3-5),
TRAC OFF light comes on.


I'm still thinking that in some capacity there is some of the auto LSD love going on in 4lo
I will mess around with 4H next time I drive it, 4hi is further down the list since I only ever use it in the snow, and it doesn't snow often here, and I'll probably drive the jeep in the snow because it's already undercoated and has aggressive tires, and is less likely to get messed up in a crash (my fault or otherwise)

 

I always assumed that ABS is passive, the system only modulates the pressure that is supplied by pressing on the master cylinder, and that traction control is active, pressure is supplied to the wheel brake assemblies without any pressure being needed from the master cylinder. Therefore, if I am correct, the brake master cylinder booster is not relevant to traction control. Anyway, looking at the Partznet parts listing, it appears that all V6 trucks have the same vacuum booster (with an engine driven vacuum pump) and master cylinders differ only between automatic and manual. There is nothing specific to off-road models. All of the 4x4 V6 trucks have, in addition, a brake pump which, presumably, supplies the pressure needed for the traction control functions. The pumps vary depending on vehicle configuration such as with or without tow package, automatic or manual, etc. but nothing is specific for the off-road version. The ABS controller (which should also control traction control) again varies by vehicle configuration, but there are now specific versions for the off-road configurations. Since the same pump is used for off-road and standard trucks with the same configuration (4x4 automatic with tow package; 4x4 automatic without tow package, 4x4 manual transmission with tow package, etc.) it appears that the traction control system (in terms of auto LSD) works on the front wheels on all 4x4 trucks. If it only worked on the off-road trucks, it would make no sense that the same brake pumps are used on off-road and standard versions. That is, if there were no LSD function on the front wheels of standard trucks, it would seem that a different brake pump would be used since there would be much less demand on it compared to the off-road version. The difference in ABS controllers may be due to an interface with the locking axle for the off-road versions, and not the LSD functions (but I really do not know). Of course, the parts listing might be incomplete, or I might be interpreting things wrong…

 

I have Trac & Auto/LSD working when in 4\low on 4X4 SR5 no VSC.




I have all on 4hi



Hope that helps
Cheers!

 

That is the VSC OFF light on in L4. Your photo does not show AUTO LSD or any TRAC function (in L4).

 

There is TRAC on the front tires in H4, so yes some brake action on the front and that is why non-off road trds do the yellow wire mod to have trac in low range, which only the off road has with its A-TRAC .

The hydraulic boosted brake unit on off road 4x4s is (or was) different than the vacuum assisted units of all other Tacomas.

 

I think I finally understand how all the various driving modes work on non-off-road or pro models. I realize this is different than some of the postings in this thread so I may be wrong, but it all seems to be logical:

VSC attempts to control vehicle stability by applying brakes selectively to individual wheels as necessary to keep the truck going where it is pointed (by steering input sensors).

Trac controls wheel spin only by reducing engine power, it has no LSD type function and does not involve the brakes in any way. Trac is intended to work with the VSC system, but because it does not use braking functions, it can be turned off independently from the VSC system. Trac is worse than useless in any serious low traction situation so it is fortunate that it can be turned off.

Auto LSD controls wheel spin on the rear axle, and only in two wheel drive, by applying brake pressure to the spinning wheel. It does not interfere with engine output. Since it is using the brakes for a function other than stability control, activating Auto LSD automatically turns off VSC (and also disables Trac).

In 4H, VSC and Trac continue to operate. But Trac only, or both Trac and VSC can be turned off at the driver’s discretion. With both off, apparently the truck is in 4 wheel drive with totally open front and rear differentials (the Auto LSD function does not seem to be activated this mode). The advantage of turning off VSC in 4H may be to reduce rolling resistance; the VSC system will not try to apply braking action when it senses the truck going off course which would be common in a rough off-road situation. Otherwise, I see no reason to turn it off if it is not enabling an LSD or A-trac function. Note: if it actually does enable an Auto LSD or A-trac type function the skid control icon should light when it is activated (has anyone seen this?).

In 4L, the symbol showing VSC off appears as soon as 4L is engaged. This cannot be changed by driver input. However, the owner’s manual makes no mention of the VSC light or function. The reason VSC is off may be because the brakes are being used for an auto LSD function on all 4 wheels (A-trac?). Again, the way to check this is to see if the skid control icon lights up in a low traction situation. If indeed an A-trac function is activated, it may be limited only to very low speeds since the manual says that A-trac in the off road version only works at 3 mph or below.

 

VSC attempts to control vehicle stability by applying brakes selectively to individual wheels as necessary to keep the truck going where it is pointed (by steering input sensors).

YES!

Trac controls wheel spin only by reducing engine power, it has no LSD type function and does not involve the brakes in any way. Trac is intended to work with the VSC system, but because it does not use braking functions, it can be turned off independently from the VSC system. Trac is worse than useless in any serious low traction situation so it is fortunate that it can be turned off.

NO: It uses engine regulation and brakes to control wheel spin and gain traction. TRAC and VSC are married, but in AUTO LSD are separated under 30 mph, then VSC goes back on. You are confusing "TRAC OFF" with TRAC "turned off" which is Toyota's fault with poor choice in naming the functions. TRAC is Traction Control (electric/ABS limited slip) and TRAC OFF (and AUTO LSD) is too, but without limiting engine output... just brakes.

Auto LSD controls wheel spin on the rear axle, and only in two wheel drive, by applying brake pressure to the spinning wheel. It does not interfere with engine output. Since it is using the brakes for a function other than stability control, activating Auto LSD automatically turns off VSC (and also disables Trac).

CLOSE: AUTO LSD is TRAC with the engine regulation turned off and this is also known as "TRAC OFF" (what it is called in H4). VSC comes on at 30 MPH. Take a drive in AUTO LSD and see the VSC OFF light go out at 30 mph.

In 4H, VSC and Trac continue to operate. But Trac only, or both Trac and VSC can be turned off at the driver’s discretion. With both off, apparently the truck is in 4 wheel drive with totally open front and rear differentials (the Auto LSD function does not seem to be activated this mode). The advantage of turning off VSC in 4H may be to reduce rolling resistance; the VSC system will not try to apply braking action when it senses the truck going off course which would be common in a rough off-road situation. Otherwise, I see no reason to turn it off if it is not enabling an LSD or A-trac function. Note: if it actually does enable an Auto LSD or A-trac type function the skid control icon should light when it is activated (has anyone seen this?).

Getting too complicated, it is easier than this. Have you read my old thread on the 9 (now 10) drive modes?

In 4L, the symbol showing VSC off appears as soon as 4L is engaged. This cannot be changed by driver input. However, the owner’s manual makes no mention of the VSC light or function. The reason VSC is off may be because the brakes are being used for an auto LSD function on all 4 wheels (A-trac?). Again, the way to check this is to see if the skid control icon lights up in a low traction situation. If indeed an A-trac function is activated, it may be limited only to very low speeds since the manual says that A-trac in the off road version only works at 3 mph or below.

A-TRAC in L4 works at any speed you can drive in low range EXCEPT when the rear is locked, then it only works if you get stuck, ie. under 3 mph.

AUTO LSD is a H2 only mode. TRAC to AUTO LSD (TRAC OFF).

In H4, you can go from TRAC to TRAC OFF (which is the same process as AUTO LSD but on 4 wheels).

The third choice in H2 and H4 is VSC OFF, which is both TRAC and VSC turned off... and only this is old fashion open differentials without electric spin controls.

In L4 the only choice for all except OFF ROAD TRDs is open differentials... unless you do the 4 LO TRAC (yellow wire) mod.

The Off Road TRDs have A-TRAC and a REAR LOCKER... They can be on separately or together. IF together, then A-TRAC works only under 3 mph.

 

I know, I know... too many functions, too many different names, too confusing!

HERE, let me make a simple (simpler?) chart of the 2009-2015 (and maybe 3rd gen too?) drive modes. All Tacomas since 2009 have #1-3. All 4x4 Tacomas since 2009 have #1-7**. All 4x4 Off Road Tacomas since 2009 have #1-10**:

IN H2 (2WD High)*:
1) Standard Mode: TRAC (limited slip using engine regulation and brake pressure)
2) Press VSC button quickly: AUTO LSD (limited slip using only brake pressure, regulation off)
3) Press and hold in button while stopped: VSC OFF (no limited slip or stability control)

IN H4 (4WD High)**:
4) Standard Mode: TRAC (limited slip using engine regulation and brake pressure)
5) Press VSC button quickly: TRAC OFF (limited slip using only brake pressure, regulation OFF)
6) Press and hold in button while stopped: VSC OFF (no limited slip or stability control)

IN L4 (4WD Low):
7) Standard Mode: VSC OFF (no limited slip or stability control)

OFF ROAD TRD ONLY:
8) Press A-TRAC button (or use MTS): A-TRAC has spin rotation matching across the axles on all 4 corners.
9) Press Rear Locker button: Locks both rear tires together for emergency stuck recovery.
10) A-TRAC & Rear Locker together: Adds rotation spin control on front tires with the rear tires locked together, when below 3 mph.

* 2WD ONLY OFF ROAD TRD also has the rear locker for emergency stuck recovery.
** 2009-2011 had no "TRAC OFF" selection or button push required for the higher level limited slip. They do no have engine regulation in H4 TRAC, only brake pressure (same as TRAC OFF or AUTO LSD)

 

The chart was just edited for clarification.

 

This is a great summary. It is strange that Toyota cannot explain it their manual.

 

I may be the only one, but I am still convinced my 2017 SR has the Auto LSD function in 4lo. I went wheeling again today, in the rain, and easily conquered a rock garden that is tough in my jeep sometimes even with lockers more aggressive tires. I am 100% sure that a rear wheel that was in the air was held still while the other one turned, verified by my buddy who was behind the truck, and me hearing the same kinda groaning sounds I've heard while wheeling land rovers with this feature. It worked well enough that it has me second guessing whether I even want to install lockers.
Maybe I should stop pushing my luck in a brand new truck, but it is fun seeing what it can do.
I'll have it back in the dirt this weekend, but the New Year's wheelin trip will be done in my jeep so I won't cry too much about new dents.

 

Was finally able to take my new 2017 SR5 4x4 off the pavement today and play around with the various 4wd modes.

Looks like when I put the truck in 4lo: a quick press of the VSC button does nothing, but a press and hold brings up "TRAC OFF." Would this then mean that the limited slip with brake pressure and no engine regulation (just like the quick-press VSC button brings up "TRAC OFF" in 4hi) is present in 4lo? I can't imagine "TRAC OFF" would mean something different between the two modes, so I've gotta believe it's accomplishing the same thing. If so, I would be even more happy with my truck and its capabilities than I already am.

 

That seems to be how it works in my truck, which has spent time in 4lo crossing both continental divides this year on some of the country's most scenic trails, in Colorado while hauling dirtbikes, as well as Tennessee and North Carolina.
I haven't gotten this truck stuck yet, even on trails where my '80 hilux had trouble on 35's, as well as having to rescue a good friend who had stuck his built Jeep.
I've had this truck right at a year next month, and have already done and seen some of the most epic places on this continent.
At least a third of the 21k miles this truck has have been in 4wd, and several thousand of these miles have been on unpaved roads.
I hope this truck will continue to serve me like this for many years to come.

 

My 2017 SR5 (non OR) does the same thing. In 4L, if I hold the VCS button I get Track off light. I'm in Kansas, flat and dry.....no place to spin a tire

 

Hello Taco community.

I honestly don't know where to even start, other than there is a lot of misinformation spread about that lead me to have some crazy ups and downs the past two weeks. I wish I wasn't so naive, but dang can it be confusing!!! I joined to say thank you to The chief and David k for sharing their experiences as they have crushed all the bad feelings I had the past two weeks since trading in my '12 TRD OR. Although it had Atrac and it was an AT. So the manual only stuff dizzies me a bit even more. But that's another story for another day.

Well, I couldn't afford the TRD OR this time around and didn't feel too bad as I thought the SR5 had a mechanical lsd. Then I was lead to believe 4lo did nothing but open diffs. Talk about being at my lowest. It never crossed my mind to go see what it actually did. I was heavily researching youtube, and the tacoma forums about these traction controls to see what I actually had for 4 wheel drive. "Open diff in the rear, please no!!!!" But even if I did try, all these traction control modes CAN be confusing. A quick press or a longer press. Toyota's manual is not comprehensive enough. So this thread actually crushed the misinformation, and all the bad feelings I had. Now I'm feeling stoked that at least, in 4lo, we have a very capable traction control system to help the open diffs. Yes, it's not a locker. My past three TRD OR's had them. I know what those can do as I used them mainly to pull people out of situations here in the Canyons of Topanga. I live at the top of a mountain, and stuff happens all the time up and down this crazy steep road. So this auto lsd might be the ticket for a controlled pull out. I don't wheel often, but tc sharing his experience made me feel alive again. Particularly the comment on how he was able to get up with street tires. That just about knocked me out with happiness.

On a side note, the 2018 safety features are nice and the dynamic cruise control is awesome. I've read that the motor lacks a sack, but to be honest, it feels so much smoother than the 4.0 and does feel strong. I haven't hit the 1,000 mile mark, so I'm itchin' to push on the pedal more. I think where I feel it more is out of a turn. A small push of the pedal and the taco gets going nicely. It always seemed like I had to push on the pedal some to get the 4.0 to go. Usually the trans dropped a gear. Maybe it's the 6 speed. Oh, and the leafs had the pads installed. I was glad to see that yesterday as I was under the Taco spot welding stuff so things won't be taken so easily.

I don't think I explained things clearly, but if anything, thank you chief and David for the comprehensive knowledge.

 

Sorry for the hiccup members. I slipped past post #5 which explains the electric booster. But here is the picture I posted




TheChief, if you stumble into the auto lsd saloon by chance, care to share how the system has handled so far? Brake wear and all. Can’t wait to go wheeling this weekend to find out how it works.

 

This Picture is of the Normal Style Vacuum Booster, not the Electro Unit Type that operates the A-TRAC or Crawl Control Systems.

 

This stuff is mind boggling. Thanks for the clarification.

 

So far everything has worked well, and at 25k miles, my brakes still look new all around, even fighting big city rush hour traffic coming home from work every day.
Sure, lockers are better, and sure true A-Trac is better, but the base model traction control does work, and I've never been stuck, even doing some things that are pretty nutty for a truck I still owe 20 grand on.
I'm a happy customer. Best money I've ever spent on a vehicle.

 

One thing that Toyota quietly included in 3rd gen Tacomas was the ability to have TRAC engaged in 4 Low. This kinda slipped under the radar for a while since it really only benefits Non-TRD off road models (those guys have ATRAC/MTS). 2nd Gen trucks had to do whats called a "yellow wire mod" in order to get some form on brake activated traction control in 4 Low. That is no longer required on 2016+ trucks. While not as effective as ATRAC, it simulates having limited slip axles front and rear. Really effective when you lose traction on two axles.