VSC / Trac Button in 2H 2015 SR5 Premium

H

hrussell

New member
Hi guys,
Recenlty picked up a 2015 SR5 Premium and been on the forums reading up on in the ins and outs of the vehicle.

One question I have is regarding the Auto LSD or lack there of feature in the SR5 Premium. My understanding is that in 2L mode when quickly pressing the overhead VSC button, the engine dethrottling is deactivated and the vehicle behaves similar to a brake enabled Auto LSD. However, the "Auto LSD" light is not illuminated - so not sure what the computer is actually doing.

If pressing and holding the Trac / VSC button, both "trac off" and VSC (swervy car icon) are displayed. My understanding is that in 2H mode, the car would now behave similar to a straight open differential (no brakes or engine dethrottling applied).

What I'm really after why the non 4x4 4Runner would display an "auto LSD" light when pressing the trac / vsc button and the 4x4 version just displays the "trac off" light.

Thanks for you help!
 
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Sorry, my mistake - should read 2H instead of 2L. Pushing the VSC / Trac button displays the "trac off" light - doesn't say anything about activating "auto LDS" as it is mentioned it will on the base 2X version.

The manual is so vague that it's of very little help. I'm guessing the sales guys at Toyota don't know too many details about the mecahnics of the vehciles. I'm sure somebody on these forums have figured out the changes from generation to generation and what exactly the buttons do and translate into a mechanical sense. Thanks.
 
hrussell said:
What I'm really after why the non 4x4 4Runner would display an "auto LSD" light when pressing the trac / vsc button and the 4x4 version just displays the "trac off" light.

Thanks for you help!
Click to expand...

Because the 2wds have auto LSDs and the 4x4s don't.
 
Thanks for the feedback.

If the 4WD versions don't have an auto LSD, what do they employ in 2H mode to limit slip (if anything). I understand that all 5th Gen 4Runners use the Open Dif and simply use braking and dethrottling (normal operational mode) to shift power from wheel to wheel on an parituclar axle.
 
hrussell said:
Thanks for the feedback.

If the 4WD versions don't have an auto LSD, what do they employ in 2H mode to limit slip (if anything). I understand that all 5th Gen 4Runners use the Open Dif and simply use braking and dethrottling (normal operational mode) to shift power from wheel to wheel on an parituclar axle.
Click to expand...

Please read the "How Does My 4WD System Work" link in my signature line.
 
1engineer said:
Exactly. 4WD has a "VSA off" button for specific situations, and yes doughnuts on snowy parking lots is one of them.
Click to expand...

Do 2014+ have VSA off? When I turn TRAC off to spin the tires the truck still gets mad at me. Some Toyotas you have hold the TRAC button to turn off VSC but I have found this is not the case in the 4runner.
 
A 4x4 in 2H mode should behave exactly as a 2 Wheel Drive 4Runner. My understading is that for the 2 Wheel Drive 4Runner, pressing the trac / vsc overhead button then illuinates the "auto lsd" dash light. Essentially all it's telling you (and it's confusing) is that engine throttling is disabled and the open differential will only be made into a limited slip diffeential via the right or left rear brake (depending on which tire is slipping). This is what Toyota calls Auto LSD.

My questions relates specifically to when the SR5 Premium (4x4) operating in 2H. When the VSC / Trac button is pressend, "trac off" is displayed and "auto LSD" is not illuminated. I can't imagine the SR5 Premium doesn't use a LSD in 2H. There is the A-TRAC feature that can be used in 4L - but that's 4L only.
 
From the Tundra forum:

The Auto LSD achieves the equivalent functions of an LSD (Limited Slip Differential) through the use of a traction control system. For this reason, the contents of brake control are the same between Auto LSD and
TRAC. When the driver presses the Auto LSD switch, this system achieves the LSD effect by regulating the hydraulic pressure that acts on the drive wheels and controlling the engine output in accordance with
the amount of pedal effort applied on the accelerator.

TRAC enhances the startoff performance of the vehicle during low-resistance surface conditions, such as snow or mud, by restricting the acceleration effort during a startoff, in order to prevent the wheels from spinning.

On the other hand, Auto LSD tends to enhance the acceleration effort somewhat, in order to apply greater drive torque to the wheel that is making contact with the ground. Thus, this function enables the vehicle to get unstuck if a wheel loses its grip, and enhances the vehicle’s startoff performance on high-resistance surface conditions such as gravel roads.

Precautions for Operating the Auto LSD:
 Operate the Auto LSD control only when the wheels are susceptible to spinning, such as when driving on a grooved, slippery, or rough surface.
 Make sure the vehicle is stopped before turning ON the Auto LSD function.
 To prevent unstable driving conditions, do not continue driving the vehicle with the Auto LSD function turned ON.
 The following conditions must be met to operate the Auto LSD system.
Auto LSD indicator light turns on when the operation enables.

i) With the vehicle stopped, the Auto LSD switch has been pressed.
(Auto LSD system operates by pushing the Auto LSD switch. Vehicle must be stopped to turn on the system. It is possible to turn off the system even if the vehicle is not stopped.)
ii) The transfer unit is in the 2WD mode.
iii) The accelerator pedal has been pressed and the vehicle is accelerating.
(The system is prohibited so as not to prevent the braking operation when depressing the brake pedal.)

 The slip indicator on the combination meter panel will blink when the Auto LSD function is operating.
 If the brake control of the Auto LSD is operated continuously, the temperature of the actuator in the hydraulic brake booster will rise.
The skid control ECU, which monitors* the temperature of the brake actuator, alerts the driver by sounding the buzzer intermittently if the brake actuator becomes overheated. In this case, the Auto LSD will momentarily stop its operation in order to protect the system.

*: Skid control ECU calculates the temperature of the brake actuator depend on the energizing time.

 The Auto LSD applies brakes to the drive wheels, and controls the extent of the brake application in order to achieve the function of an LSD. However, it might not be able to achieve this function on a steep incline or on an extremely slippery surface, such as a frozen snow surface.
 
hrussell said:
A 4x4 in 2H mode should behave exactly as a 2 Wheel Drive 4Runner. My understading is that for the 2 Wheel Drive 4Runner, pressing the trac / vsc overhead button then illuinates the "auto lsd" dash light. Essentially all it's telling you (and it's confusing) is that engine throttling is disabled and the open differential will only be made into a limited slip diffeential via the right or left rear brake (depending on which tire is slipping). This is what Toyota calls Auto LSD.

My questions relates specifically to when the SR5 Premium (4x4) operating in 2H. When the VSC / Trac button is pressend, "trac off" is displayed and "auto LSD" is not illuminated. I can't imagine the SR5 Premium doesn't use a LSD in 2H. There is the A-TRAC feature that can be used in 4L - but that's 4L only.
Click to expand...
Correct. Are you typing on a phone or something? Anyway, when VSC is depressed the brakes still act to give you the pseudo LSD for both rear wheels if one spins. No throttle r e t a r d a t i o n though. My light just showed VSC off. Now, the VSC also does a whole bunch of other dynamic stuff but for your specific question (I think) this should answer it. Why do you ask?
 
Good answers, thanks. The one thing that still baffles me is why auto LSD is displayed when trac /vsc is disabled on the 2WD 4Runner and "trac off" is illuminated when trav / vsc is disabled on the 4x4 4Runner.

All 4Runners (I believe) only use Open Differentials on the drive axles (with the exception of the Limited that uses a center diff to distribute power front to rear). Instead of using a mechanical (viscous or clutch based LSD) LSD, Toyota employed the brakes to enhance traction (left wheel vs right wheel) regardless of what version of the 4Runner is purchased.

As previosly mentioned, the 4x4 4Runner doesn't use Auto LSD. Therefore what do they use if anything in 2H mode (A-Trac is reserved for 4L)? I assume they do still use an "auto LSD" but trying to confirm this isn't easy.

And yes, all braking and engine dethrottling can be disabled by pressing and holding the VSC / Trac button for 3 more seconds.
 
hrussell said:
Good answers, thanks. The one thing that still baffles me is why auto LSD is displayed when trac /vsc is disabled on the 2WD 4Runner and "trac off" is illuminated when trav / vsc is disabled on the 4x4 4Runner.

All 4Runners (I believe) only use Open Differentials on the drive axles (with the exception of the Limited that uses a center diff to distribute power front to rear). Instead of using a mechanical (viscous or clutch based LSD) LSD, Toyota employed the brakes to enhance traction (left wheel vs right wheel) regardless of what version of the 4Runner is purchased.

As previosly mentioned, the 4x4 4Runner doesn't use Auto LSD. Therefore what do they use if anything in 2H mode (A-Trac is reserved for 4L)? I assume they do still use an "auto LSD" but trying to confirm this isn't easy.

And yes, all braking and engine dethrottling can be disabled by pressing and holding the VSC / Trac button for 3 more seconds.
Click to expand...

How about this: On 4Runner 4WD, in 2HI, both rear wheels will spin on a slick surface when applying throttle before the throttle cuts. With VSC off, both rear wheels will again spin with no throttle cut. How? Selective braking. What do they call it? VSC "off." Why is is different between 2WD vehicles and 4WD vehicles? It could be marketing, competition, different departments working on the drivetrain, using up old inventory, who knows. This has to answer your question.
 
st8rocks said:
Do 2014+ have VSA off? When I turn TRAC off to spin the tires the truck still gets mad at me. Some Toyotas you have hold the TRAC button to turn off VSC but I have found this is not the case in the 4runner.
Click to expand...

Hold the Trac button down for 3 seconds while stopped and the Trac Off and the VSC Off in the dash will light therefore be disengaged.... IIRC!
I hope that was what you were referring to!
 
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The "auto lsd" on 2WD models seems to be a creation by product marketing to add "features" to the 2WD product.

If you were to take both a 2WD and a 4WD (not a limited and in 2WD) 4runner and test WOT acceleration on a wet 90 degree right hand turn from a dead stop they would both behave exactly the same way.
 
Got it, thanks. The marketing and terminology behind something quite simple makes things simple appear different and thus confusing. I've made assumptions on the way I would imagine they work - just nice to have confirmation less taking the 4Runner Off Roading to verify / test traction ability and scenarios. Thanks!
 
hrussell said:
Got it, thanks. The marketing and terminology behind something quite simple makes things simple appear different and thus confusing. I've made assumptions on the way I would imagine they work - just nice to have confirmation less taking the 4Runner Off Roading to verify / test traction ability and scenarios. Thanks!
Click to expand...

Here is a great explanation of both 2 and 4WD vehicles. It's a bit old and for the FJ but it's the same. VSC, A-TRAC, ABS & Diff Lock Explained - Toyota FJ Cruiser Forum
 
Exactly. Marketing hype calling the exact same system (in essence) something different using the same owners manual confusing the heck out of people who have a limited mechanical knowledge of how drive train's function. I agree with you Donkey - it's all marketing hype to try and sell. Albeit, the system itself works pretty well.
 
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