When wheel slip is noted during a brake application, the ABS enters antilock mode. During antilock braking, hydraulic pressure in the individual wheel circuits is controlled in order to prevent any wheel from slipping. A separate hydraulic line and specific solenoid valves are provided for each wheel. The ABS can decrease, hold, or increase hydraulic pressure to each wheel brake. However, the ABS cannot increase hydraulic pressure above the amount which is transmitted by the master cylinder during braking.

During antilock braking, a series of rapid pulsations will be felt in the brake pedal. These pulsations are caused by the rapid changes in position of the individual solenoid valves as they respond to their desired wheel speed. This pedal pulsation is present during antilock braking and stops when normal braking is resumed or when the vehicle comes to a stop. A ticking or popping noise may also be heard as the solenoid valves rapidly cycle. During antilock braking on dry pavement, the tires may make intermittent chirping noises as they approach slipping. These noises and pedal pulsations should be considered normal during antilock operation.

The vehicle may be stopped by applying normal force to the brake pedal. Brake pedal operation during normal braking should be no different than previous systems. Maintaining a constant force on the pedal will provide the shortest stopping distance while maintaining vehicle stability.

The Dynamic Rear Proportioning (DRP) is a control system that replaces the hydraulic proportioning function of the proportioning valve in the base brake system. The DRP control system is part of the operation software in the EBCM. The DRP uses active control with existing ABS in order to regulate the vehicle's rear brake pressure.

DTC C1248 sets in order to indicate that the EBCM illuminated the red BRAKE warning indicator. The EBCM cannot perform DRP due to another fault in the ABS/TCS system. DTC C1248 will never set by itself.

When the EBCM senses a wheel slip, the EBCM isolates the system by closing the inlet valve and keeping the outlet valve closed in the brake pressure modulator valve (BPMV). This holds the pressure steady on the brake so hydraulic pressure does not increase or decrease.

If during the pressure hold mode, the EBCM still senses wheel speed slip, the EBCM decreases pressure to the brake by leaving the inlet valve closed and opening the outlet valve in the BPMV. The excess fluid is stored in the accumulator until the fluid can be returned to the reservoir by the return pump.

If during the pressure hold or decrease mode, the EBCM senses that the wheel speed is too fast, the EBCM increases pressure to the brake by opening the inlet valve and closing the outlet valve in the BPMV. The increased pressure comes from the master cylinder and is related to the pressure applied to the brake pedal.

Traction control does not have any effect on the operation of the vehicle until the control module detects one or both of the front wheels rotating faster than the rear wheels. At this time, the electronic brake control module (EBCM) requests the powertrain control module (PCM) to reduce the amount of torque applied to the drive wheels. The PCM does this by retarding timing and selectively turning off fuel injectors (up to a maximum of 3). The EBCM applies the front brakes, thus reducing torque to the front wheels. Once the front wheels begin to rotate at the same speed as the rear wheels, the system returns full control to the driver. During Traction Control mode, if the brake is applied to only one front wheel, most of the torque from the engine is directed to the other front wheel which improves the traction of the vehicle.

The braking is accomplished by closing the TCS master cylinder isolating valves, this isolates the master cylinder from the rest of the system. The TCS prime valves open in order to allow the pump to get brake fluid to build pressure for braking. The drive wheel circuit solenoids are energized as needed to allow for the following conditions:

The TCS may be deactivated by the driver, if desired. In order to deactivate the TCS with the engine running, depress the traction control disable switch. The system will remain deactivated until the ignition switch is cycled, or the switch is pressed again.

The vehicle stability enhancement system (VSES) involves the Integrated Chassis Control System (ICCS3 for this vehicle). It includes an additional level of control to the EBCM. The VSES monitors the wheel speeds, lateral acceleration and steering sensor inputs to calculate a desired yaw rate, and compare the inputs to the actual yaw rate reported by the yaw rate sensor. Steering maneuvers can cause the desired yaw rate to differ from the reported yaw rate by some amount. This difference can result from tire compliance, suspension compliance, and wheel slip. The VSES tries to bring these yaw rates into agreement by selectively applying the front wheel brakes. This is known as active brake control (ABC). If wheel slip rates are excessive, traction control may activate to reduce power.

The speed dependent steering system (Magna Steer®) incorporates its controller into the EBCM. The DTC C1241 will not cause any indicators or messages to turn on. Refer to Variable Effort Steering Description in Variable Effort Steering.

When using the compact spare tire, the spare tire will rotate faster than the other tires. The EBCM will compensate for this faster tire rotation.

The red BRAKE warning indicator in the instrument cluster illuminates to warn the driver of conditions in the brake system which may result in reduced braking ability. The indicator stays illuminated until the condition has been repaired. The following conditions will cause the red BRAKE warning indicator to illuminate:

The ABS indicator is located in the instrument cluster and illuminates if a malfunction in the ABS is detected by the EBCM. The ABS indicator informs the driver that a condition exists which results in disabling ABS. If only the ABS indicator is on, normal braking with full power assist is available. If the BRAKE and ABS indicators are on, a problem may exist in the hydraulic brake system. The following conditions will cause the ABS indicator to illuminate:

Illumination of the BRAKE warning Indicator may indicate reduced braking ability. Illumination of the ABS indicator without the BRAKE warning Indicator ON indicates only that ABS braking is no longer available. Power assisted braking without ABS control is still available. Refer to Brake System Diagnosis in Hydraulic Brakes for diagnosis of any condition which causes the BRAKE warning Indicator to illuminate.

The following conditions will cause the TRACTION OFF indicator to illuminate:

The indicator is controlled by the instrument cluster via class 2 serial messages from the EBCM. There are no hard wires involved in the indicator control.

The following messages, related to the DRP/ABS/TCS/TIM/VES/VSES may be displayed on the driver information center (DIC).