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.
The primary function of the Traction Control System (TCS) is to optimize vehicle performance with varying vehicle load and changing road conditions by controlling wheel slip at the driven wheels during an acceleration maneuver. The wheel slip is controlled by actively applying braking force. This modulation is applied and occur under all throttle input conditions where the difference between wheel speed' and vehicle speed indicate a loss of longitudinal traction.
TCS operation for each mode of driveline operation include the following. When high range is selected for the transfer case, the system controls wheel slip in the order of stability and acceleration. When low range is selected for the transfer case, the system controls wheel slip in the order of acceleration and stability.
A traction mode switch (TC2) is included to improve traction system performance on loose surfaces. The mode switch will have a momentary action and resets when the switch is pressed again or the ignition is cycled. The switch will have two states, one state is Road, and the other state is Loose Surface. When the switch is in the Road mode, the traction system will preform at its maximum, and in the loose surface mode will be adjusted for road conditions.
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 IPC illuminates the ABS indicator when the following occurs:
The IPC illuminates the BRAKE indicator when the following occurs:
The IPC illuminates the traction assist indicator when the following occurs:
The EBCM illuminates the LED indicator, part of the TC2 switch, when the following occurs:
