Antilock Brake System With Electronic Stability Program (ESP)

ELECTRONIC STABILITY PROGRAM

Electronic Stability Program (ESP(R)), which includes Hydraulic Brake Assist, Traction Control, Electronic Roll Mitigation, and Brake Lock Differentials is standard on all vehicles. ESP(R) aids the driver in maintaining vehicle directional stability. ESP will do whatever can be done, within the limits of available traction, to keep the car on course.

ESP(R) uses the ABS with Traction Control (MK25E) along with the following components to operate:

- Dynamics (ESP) Sensor
- Steering Angle Sensor (SAS)

The Dynamics Sensor that is mounted under the center console, which is near the center of gravity of the car for effective sensing Description and Operation. The Steering Angle Sensor is located in the steering column Description and Operation.

On this vehicle, ESP(R) has three modes: Full-On, Partial and Full-Off. The ESP(R) default mode is Full-On with every key-on. Pressing the ESP Off switch button in the center stack once activates the Partial mode. In Partial mode, Traction Control is deactivated and ESP(R) operates at a higher threshold, therefore, it will not come on as aggressively as in the Full-On mode. Pressing and holding the ESP Off switch button for five seconds or longer turns the system completely off. This condition is confirmed by a single warning chime and a text message in the odometer display "ESP FULL OFF." The system can be returned to "normal" Full-On mode by briefly pressing and releasing the ESP Off switch.

HYDRAULIC BRAKE ASSIST

Brake Assist is programmed into the ESP(R) system. Brake assist helps the driver overcome the tendency to not apply the brakes hard enough or quick enough to achieve the minimum stopping distance during a panic stop. During this situation, the ESP(R) system instantly applies the maximum available pressure to the brakes and the vehicle stops as quickly as available traction will allow.

TRACTION CONTROL

For information on the All-Speed Traction Control, Description and Operation.

ELECTRONIC ROLL MITIGATION

ESP(R) Full-On and Partial modes include an algorithm for Electronic Roll Mitigation (ERM). ERM is an algorithm on top of ESP(R) control that is targeted toward preventing wheel lift in the NHTSA Fish Hook maneuvers. These very extreme situations are well out of normal everyday driving, but by chance a high dynamic maneuver occurs, ERM can help return vehicle stability and control to the driver. Electronic Roll Mitigation attempts to determine when a vehicle is in a position to mitigate vehicle rollover and minimize the risk by applying the appropriate braking force to reduce the likelihood that such an event will occur. This added measure is designed to aid the driver in maintaining vehicle stability during an emergency maneuver or accident avoidance situation. ERM will not aid vehicle stability in "trip" situations, such as when a vehicle slides sideways and strikes a curb, which could then cause the side opposite the curb to lift and the vehicle to roll.

BRAKE LOCK DIFFERENTIALS

Brake Lock Differentials (BLDs) are part of the ESP(R) base algorithm and tuned for on-road activity. Brake Lock differentials improve vehicle mobility by applying braking force to a driven wheel that is spinning faster than the mate on the same axle to provide an equal amount of torque for each wheel, thereby providing torque to the wheel with the most traction. The on-road BLD is calibrated for on-road conditions such as when one wheel is on ice or gravel and the other is on dry pavement, this type of condition is called a split-friction surface.

Vehicles equipped with the Off-Road Group (sales code AWL) include a separate set of BLD calibrations that are designed for Off-Road mode use while crawling over obstacles, during heavy articulation activity, split-friction surfaces and other conditions. Off-Road BLDs direct torque from the wheel that slips to the wheel with more grip on a given axle helping maintain forward mobility over all types of off-road terrain.

Off-Road BLD calibrations are activated when the vehicle is in the Off-Road mode. The Off-road calibration applies much more aggressive and longer duration brake caliper clamping than the calibration for on-road BLDs to achieve the desired performance over off-road events.

HILL DESCENT CONTROL

Hill Descent Control (HDC) is included on vehicles equipped with the Off-Road Group (sales code AWL). It provides downhill assistance at a safe and controlled rate of speed without requiring the driver to touch the brakes or press a button. This feature operates in low and reverse gears. By means of electronics it replaces the gear reduction and engine braking that a traditional mechanical low-range transfer case provides. For ease of operation, HDC is activated and deactivated automatically according to changes in topography using grade sensing.