Electronic Stability Program

Electronic Stability Program

The electronic stability program (ESP) enhances control and stability under various driving conditions. ESP corrects for over/under steering by applying the brake of the appropriate wheel to assist in counteracting the over/under steer condition. Engine power may also be reduced to help maintain the desired path. ESP uses sensors to determine the vehicle path intended by the driver and compares it to the actual path. When the actual path does not match the intended path, ESP applies the brake of the appropriate wheel to assist in counteracting the over steer or under steer condition.

• Over steer - When the vehicle is turning more than appropriate for the steering wheel position.

• Under steer - When the vehicle is turning less than appropriate for the steering wheel position.

The ESP/TCS indicator lamp located in the instrument cluster starts to flash as soon as the tires lose traction and the ESP system becomes active. The ESP/TCS indicator lamp also flashes when the TCS is active.

The ESP default mode is FULL-ON with every key-on. Pressing the ESP OFF button once activates what is referred to as Partial mode. In Partial mode, traction control is deactivated and ESP operates at a higher threshold, therefore, it will not come on as aggressively as in the FULL-ON mode. The system can be returned to "normal" FULL-ON mode by pressing and releasing the ESP OFF switch. The ESP function lamp is illuminated in the cluster whenever the ESP system is turned off.

To determine whether the car is responding properly to cornering commands, ESP uses steering wheel angle, yaw (turning) rate and lateral acceleration sensors (combined into dynamics sensor). Using signals from these sensors, in addition to individual wheel speed sensor signals, the system determines appropriate brake and throttle actions. Once initiated, ESP operates much like all-speed traction control, except that the goal is directional stability. If the vehicle yaw response, or rate of turning, is inconsistent with the steering angle and vehicle speed indications, the ESP system applies the brakes and, if necessary closes the throttle, to restore control. This occurs whether the vehicle is turning too rapidly (over steering) or not rapidly enough (under steering).