The vehicle may be equipped with the following braking systems:
The following components are involved in the operation of the above systems:
The electronic brake control module (EBCM) performs one initialization test each ignition cycle.
The initialization sequence may also be commanded with a scan tool.
The initialization sequence cycles each solenoid valve and the pump motor, as well as the necessary relays for approximately 1.5 seconds to check component operation. The EBCM sets a DTC if any error is detected. The initialization sequence may be heard and felt while it is taking place, and is considered part of normal system operation.
The EBCM defines a drive cycle as the completion of the initialization sequence.
When wheel slip is detected during a brake application, the ABS enters antilock mode. During antilock braking, hydraulic pressure in the individual wheel circuits is controlled 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. The ABS cannot, however, increase hydraulic pressure above the amount which is transmitted by the master cylinder during braking.
During antilock braking, a series of rapid pulsations is felt in the brake pedal. These pulsations are caused by the rapid changes in position of the individual solenoid valves as the electronic brake control module (EBCM) responds to wheel speed sensor inputs and attempts to prevent wheel slip. These pedal pulsations are present only during antilock braking and stop 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 cycle rapidly. During antilock braking on dry pavement, intermittent chirping noises may be heard as the tires approach slipping. These noises and pedal pulsations are considered normal during antilock operation.
Vehicles equipped with ABS may be stopped by applying normal force to the brake pedal. Brake pedal operation during normal braking is no different than that of previous non-ABS systems. Maintaining a constant force on the brake pedal provides the shortest stopping distance while maintaining vehicle stability.
The electronic brake control module (EBCM) closes the hold valve and keeps the reduction valve closed in order to isolate the system when wheel slip occurs. This holds the pressure steady on the brake so that the hydraulic pressure does not increase or decrease.
The electronic brake control module (EBCM) decreases the pressure to individual wheels during a deceleration when wheel slip occurs. The hold valve is closed and the reduction valve is opened. The excess fluid is stored in the accumulator until the return pump can return the fluid to the master cylinder.
The electronic brake control module (EBCM) increases the pressure to individual wheels during a deceleration in order to reduce the speed of the wheel. The hold valve is opened and the reduction valve is closed. The increased pressure is delivered from the master cylinder.
The electronic brake force distribution (EBD) system is part of the operation software in the electronic brake control module (EBCM). The EBD uses active control with existing ABS in order to regulate the vehicle's front to rear brake pressure.
The traction control system (TCS) is designed to limit wheel slip during acceleration when one or more of the drive wheels are accelerating too rapidly. Traction control will not have any effect on vehicle operation until the electronic brake control module (EBCM) detects one or both of the front wheels rotating faster than the rear wheels. The TCS accomplishes this by 2 methods, engine torque reduction and brake intervention. The 2 methods are used together to control wheel slip during acceleration. Both methods are described below.
The vehicle stability enhancement system (VSES) is also known as the Stabilitrak Plus system, and the instrument cluster indicator lamp is labeled Stability Off. The VSES consists of a yaw/lateral accelerometer sensor, a steering angle sensor, and a brake pressure sensor working in conjunction with the electronic brake control module (EBCM).
The yaw rate sensor and deceleration sensor are both in the same module. The yaw/deceleration sensor is located under the front - LH seat.
The steering angle sensor sends dual controller area network (CAN) signals to the EBCM. The EBCM determines steering wheel position and rotation using these signals.
The EBCM uses input from the brake pressure sensor for more accurate control during a VSES event.
The instrument panel cluster (IPC) illuminates the ABS indicator when the following occurs:
The instrument panel cluster (IPC) illuminates the Low Trac indicator when the following occurs:
The instrument panel cluster (IPC) illuminates the Stability System indicator when the following occurs:
The instrument panel cluster (IPC) illuminates the brake indicator when the following occurs: