As there seem to be quite a few questions lately about the drive control systems and buttons on the 4.3 RAV4, I thought I would create a thread for the specific purpose of providing an overview explanation of these systems. Maybe it could become a "sticky?"
I'll start with how I understand the systems to work, at least for North American models, and others can please chime in with additional information. I'll edit this first post with additional information as appropriate.
("Active Torque Control" System)
The 4WD system on the 4.3 RAV4 is called "Active Torque Control." In the 4.4 RAV4 it got renamed to "Dynamic Torque Control" but it is the same system with the additional awareness of Sport mode, which was new on the 4.4 models.
Under normal circumstances the 4WD RAV4 operates in front wheel drive mode for increased fuel efficiency, with the rear wheels getting some portion of power only when it is detected this is beneficial to the vehicle. For example, if the front wheels start to slip. I've read that the detection process typically takes something on the order of 6 milliseconds.
Here is the ATC description from page 194 of the 2012 RAV4 owner's manual:
Automatically switches from front-wheel drive to four-wheel drive (4WD) according to the driving conditions, helping to ensure reliable handling and stability. Examples of conditions where the system will switch to 4WD are when cornering, going uphill, starting off or accelerating, and when the road surface is slippery due to snow, rain, etc.
A much more in-depth description of the 4WD system in the RAV4 can be found in this Toyota document
This link from Toyota allows interactively exploring the various 4WD systems they offer, including for the RAV4: http://www.majormedia2.com/4WDSimplifiedv5/4WD.html
This is one of the so-called "nannies" which may reduce power to the wheels. The 2012 RAV4 owners manual has this to say about TRAC:
Maintains drive power and prevents the drive wheels from spinning when starting the vehicle or accelerating on slippery roads.
This will reduce power to slipping wheels in order to improve the odds that they'll be able to get traction.
VSC and Enhanced VSC
(Vehicle Stability Control)
These are more of the so-called "nannies" which may reduce power to the wheels. The 2012 RAV4 owners manual has this to say about VSC and Enhanced VSC:
VSC - Helps the driver to control skidding when swerving suddenly or turning on slippery road surfaces.
Enhanced VSC - Provides cooperative control of the Anti-lock Brake System (ABS), TRAC, VSC and Electric Power Steering (EPS). Helps to maintain directional stability when swerving on slippery road surface by controlling steering performance.
This is accomplished at least in part by using accelerometer sensors in the front and rear of the vehicle and sensors in the steering. If the accelerometers indicate the vehicle is not moving in the direction the front wheels are pointing (e.g. the vehicle is yawing) this system will kick in to control power to various wheels to help the vehicle move in the direction the steering is pointing.
(Downhill Assist Control, located to the left of the steering wheel)
This button is used to turn on or off the DAC system, which is available only in the 4.3 models with the V6 engine and all 4.3 models with the 3rd-row seat (as of this writing it's not available on the 4.4 models). This system, which some have hailed as little short of miraculous, forces the vehicle to crawl down a steep/slippery hill at approximately 3 MPH (5 KPH) by individually applying varying brake pressures to each of the 4 wheels.
This system can only be turned on when the vehicle is moving at less than 15 MPH (25 KPH) [stopped is preferred?] and the shift lever is either in L (low) or R (reverse). When on, the DAC light on the dashboard will light up steady. If the DAC button is pressed while using the system, the light flashes and the system gradually ceases operation. The light will go out when the system goes off.
The system will automatically turn off if:
- The brake pedal is depressed
- The accelerator pedal is depressed
From the owner's manual, here is what the DAC button and instrument panel light look like:
4WD Lock Button
(Located to the left of the radio)
When pressed, the Lock button "locks" power 55% to the front wheels and 45% to the rear wheels at speeds up to 25 MPH (40 KPH). A light on the dashboard stays illuminated when this system is manually turned on, and goes off above 25 MPH to indicate the system is off, or if the button is pushed again to turn it off. If this light ever flashes, it means there is a problem with the 4WD system.
While the owner's manual states that the system will turn off if the brakes are applied "to ensure the ABS and VSC systems operate effectively," this does not appear to be the case in my RAV4. I tested it today, and the lock stayed on when I pressed the brake pedal.
This button is primarily intended for the driver to help get the vehicle unstuck. The RAV4 has no way for the driver to force the system to continuous 4WD mode at speeds above 25 MPH. While this is ostensibly to maintain increased fuel economy, some have theorized it's also to prevent over-stressing the components with the shock loads that could occur at higher speeds.
From the owner's manual, here is what the 4WD Lock button and instrument panel light look like:
TRAC Off Button
(Located in front of the front left cup holder, 2009 and newer models)
Pressing this button momentarily will turn off the traction control system. When off, the "TRAC OFF" indicator light will appear on the dash. Pressing the button again will reactivate the TRAC system. The TRAC system will come back on automatically when the vehicle speed increases, or the vehicle is restarted.
Pressing and holding this button for a few seconds while the vehicle is stopped will turn off both
the TRAC system and the VSC system. The "TRAC OFF" and VSC Off indicator lights will appear on the dash. Pressing the button again will reactivate these systems. These systems will also come back on again the next time the vehicle is restarted, but neither will come back on if the vehicle speed increases.
From the owner's manual, here is what the TRAC Off button looks like, as well as the lights for both TRAC Off and VSC Off:
To accomplish this for 2006 - 2008 models, a process affectionately known as the "brake dance
" must be used.
What to do if stuck in snow or mud, or to help prevent getting stuck
If stuck in snow or mud, generally the best thing to do is turn on the 4WD Lock system and turn off the nannies (both the VSC and TRAC systems), as described above. Turning the nannies off, particularly TRAC, allows rocking back and forward to more forcefully to get unstuck.
Though as Dr. Dyno recently stated in another post (click here
for full context): The 4WD systems in our RAV4s aren't heavy duty like a 4X4 truck so be careful when disabling the electronic nannies, part of whose purpose is to protect the lighter duty components. That's probably also why 4WD LOCK goes off at 25 mph.
Hill Assist Control (HAC)
(Using the brake pedal)
This system is also sometimes called Hill Start Assist (HSA). The owner's manual has this to say about HAC:
Hill Start Assist Control (HAC) is designed to help minimize backward rolling on steep ascents.
This allows the driver to move their foot from the brake pedal to the gas pedal without the vehicle rolling as they are moving their foot.
HAC can be activated by very firmly pressing the brake pedal for a few seconds. A single beep and flashing indicator on the instrument panel will indicate the HAC system is active. When the driver eventually lifts their foot off the brake pedal, the brakes will remain engaged for 2 to 3 seconds and will then release, allowing the vehicle to move. A single beep is heard when the brakes release and the light on the instrument panel will turn off. Here is a YouTube video demonstrating HAC in the RAV4
From the owner's manual, this light (the same as the VSC light) will appear on the instrument panel when HAC is being used:
Much more in-depth descriptions of the ABS, VSC, TRAC, EBD, HAC, DAC and Auto LSD (for 2WD RAV4s) can be found in this Brake Control System document
. (Thanks again, JuneBug!)