This vehicle is equipped with the Bosch 5.3 antilock braking system.
The vehicle is equipped with the following braking systems:
The following components are involved in the operation of the above systems:
The EBCM performs one initialization test each ignition cycle. The initialization of the EBCM occurs when one set of the following conditions occur:
Both of the following conditions occur:
OR
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 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 EBCM closes the inlet valve and keeps the outlet 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 EBCM decreases the pressure to individual wheels during a deceleration when wheel slip occurs. The inlet valve is closed and the outlet valve is opened. The excess fluid is stored in the accumulator until the return pump can return the fluid to the master cylinder.
The EBCM increases the pressure to individual wheels during a deceleration in order to reduce the speed of the wheel. The inlet valve is opened and the outlet valve is closed. The increased pressure is delivered from the master cylinder.
The dynamic rear proportioning (DRP) is a control system that replaces the hydraulic proportioning function of the mechanical 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.
The red brake warning indicator is illuminated when the dynamic rear proportioning function is disabled.
Traction control will not have any effect on the operation of the vehicle until the control module detects one or both of the rear wheels rotating faster than the front wheels. At this time the Electronic Brake and Traction Control Module (EBCM) will request the Powertrain Control Module (PCM) to retard timing. If the EBCM continues to detect the rear wheel are rotating faster than the front it will request the ASM to reduce the throttle angle. The last measure taken to control the rear wheel is for the EBCM to apply the rear brakes, thus reducing torque to the rear wheels. Once the rear wheels begin to rotate at the same speed as the front wheels, the system will return full control to the driver. During Traction Control mode, if the brake is applied to only one rear wheel, most of the torque from the engine will be directed to the other rear wheel which will improve the traction of the vehicle.
The braking is accomplished by closing the TCS Master Cylinder Isolating Valve, this isolates the master cylinder from the rest of the system. The TCS Prime valve opens 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 pressure hold, pressure increase, or pressure decrease.
The TCS may be deactivated by the driver if desired. In order to deactivate the TCS with the engine running, depress the TCS On/Off switch. The system will remain deactivated until the ignition switch is cycled, or the switch is pressed again.
The IPC illuminates the ABS indicator when the following occurs:
The IPC illuminates the BRAKE indicator when the following occurs:
The IPC illuminates the Low Trac indicator when the following occurs:
The IPC illuminates the indicator when the following occurs:
