Anti-Lock Control - Stability Assist: Introduction: Notes

The ABS modulates brake pressure on each wheel independently to maintain vehicle stability during braking. The ABS continually monitors the rotational velocity of each wheel during driving and determines if a tire is skidding when the brakes are applied. Only then does the ABS intervene to modulate the brake pressure to the skidding wheel. The modulation continues until the wheel rotates freely. The brake pressure is then restored and the modulate/restore cycle is repeated whenever skidding is detected. This cycle occurs at a rate of several times per second.

The ABS control module is capable of detecting the following system conditions:

• Hydraulic valve failure
• Wheel speed sensor failure
• ABS power relay short circuit
• Interconnect failures to the ABS sensors, power and ground to the ABS module
• Over/under voltage conditions

The ABS provides self-diagnostics and displays failure messages through the ABS warning indicator in the instrument cluster. Failure of the ABS module, for whatever reason, will not compromise the normal operation of the brake system.

The DSC system includes the:

• anti-lock brake system
• lateral/yaw control
• full speed traction control

The DSC system manages the braking system to enhance the driver control of the vehicle.

The DSC system continually monitors the steering wheel angle, master cylinder brake pressure, front and rear wheel speeds and vehicle lateral/yaw rate acceleration.

The lateral/yaw rate sensor supplies a signal to the DSC module, via a serial link, which monitors the vehicles rate of acceleration from its central axis in a sideways direction, and also the vehicles angular rotation around its central axis.

The driver input parameters are continually monitored by the steering wheel rotation sensor and the hydraulic control unit master cylinder pressure sensor.

The DSC is enabled/disabled through the traction control ON/OFF switch.

Self-diagnosis of the DSC system is provided through the instrument cluster and message center.

Traction control is an additional function added to the ABS/DSC system. The vehicles driven wheels are continually monitored for wheel spin relative to the calculated reference speed and to each other. If wheel spin is detected, the traction control function intervenes independently of the driver, applying brake pressure to the spinning wheel and reducing the engine drive torque supply. Meanwhile, brake pressure is modulated by the traction control until traction is re-established. Traction control brake actuation is diminished above 40 kph (25 mile/h). Above this speed, traction control relies primarily on engine torque reduction.

Traction control is enabled/disabled through the traction control ON/OFF switch. When the switch is in the OFF position, the amber traction control warning lamp solidly illuminates within the instrument cluster message center. The traction control is automatically activated when the ignition is switched on. Self-diagnosis of the traction control system is also provided through the instrument cluster and message center.

The traction control brake intervention is automatically disabled whenever the brakes exceed a temperature limit. The traction brake intervention will remain disabled until the brakes have cooled.