"Vehicles with RPO JL4 are equipped with an EBC 445V ABS/DRP/TCS/VSES module.
This module provides the following vehicle performance enhancement systems.
*Antilock Brake System (ABS)
*Dynamic Rear Proportioning (DRP)
*Traction Control System (TCS)
*Vehicle Stability Enhancement System (VSES)
The following components are involved in the operation of the above systems.
*Electronic brake control module (EBCM)--the EBCM controls the system functions and detects failures.
The EBCM contains the following components.
-System relay--The system relay is internal to the EBCM. The system relay is energized when the ignition is ON. The system relay supplies battery positive voltage to the valve solenoids and to the abs pump motor. This voltage is referred to as system voltage.
-Solenoids--The solenoids are commanded ON and OFF by the EBCM to operate the appropriate valves in the brake pressure modulator valve (BPMV)
-Longitudinal accelerometer--The EBCM uses the longitudinal accelerometer to determine the actual straight-line acceleration of the vehicle.
*BPMV--The BPMV uses a 4-circuit configuration to control hydraulic pressure to each wheel independently.
The BPMV contains the following components.
-ABS pump motor and pump
-Four isolation valves
-Four dump valves
-Two TC isolation valves
-Two TC supply valves
-A master cylinder pressure sensor
-A front low-pressure accumulator
-A rear low-pressure accumulator
*Wheel speed sensors (WSS)--As the wheels spin, toothed rings interrupt magnetic fields in the wheel speed sensors. This causes each wheel speed sensor to generate an AC signal. The EBCM uses these AC signals to calculate the wheel speed. Any imperfections in the toothed ring, such as a missing or damaged tooth, can cause an inaccurate WSS signal.
*Traction control switch--VSES and the engine torque reduction function of TCS are manually disabled by pressing and holding the traction control switch for at least 5 seconds. These functions can be re-enabled with a quick press and release of the TC switch.
*Lateral accelerometer--The EBCM uses the lateral accelerometer to determine the sideways acceleration of the vehicle. The lateral accelerometer is packaged with the yaw rate sensor as a single component.
*Master cylinder pressure sensor--The master cylinder pressure sensor is located within the BPMV. The master cylinder pressure sensor uses a 5-volt reference and generates an output signal proportionate to the hydraulic fluid pressure which is present in the front brake circuit at the master cylinder.
*Yaw rate sensor--The EBCM uses the yaw rate sensor to determine the rate of rotation along the vehicle's vertical axis. The yaw rate sensor is packaged with the lateral accelerometer as a single component.
*Steering wheel position sensor--The EBCM receives several inputs from the steering wheel position sensor. Three digital square wave signal inputs are wired directly to the EBCM harness connector, however, only signals A and B are used or monitored. The failure of the index pulse signal does not affect VSES function. The EBCM also monitors an analog steering wheel position sensor signal. Battery voltage is supplied to the digital portion of the steering wheel position sensor by the ignition 1 circuit. The analog portion of the steering wheel position sensor is supplied by a 5-volt reference from the EBCM.
ANTILOCK BRAKE SYSTEM (ABS)
When wheel ship is detected during a brake application, an ABS event occurs. During antilock braking, hydraulic pressure in the individual wheel circuits is controlled to prevent any wheel from slipping. A separate hydraulic ling and specific solenoid valves are provided for each wheel. the ABS can decrease, hold, or increase hydraulic pressure to each wheel. The ABS does not, 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 that that of previous non-ABS systems. Maintaining a constant force on the brake pedal provides the shortest stopping distance while maintaining vehicle stability. The typical ABS activation sequence is as follows.
Pressure Hold
The EBCM closes the isolation valve and keeps the dump valve closed in order to isolate the slipping wheel when wheel slip occurs. This holds the pressure steady on the brake so that the hydraulic pressure does not increase or decrease.
Pressure Decrease
If a pressure hold does not correct the wheel slip condition, a pressure decrease occurs. The EBCM decreases the pressure to individual wheels during deceleration when wheel slip occurs. The isolation valve is closed and the dump valve is opened. The excess fluid is stored in the accumulator until the pump can return the fluid to the master cylinder or fluid reservoir.
Pressure Increase
After the wheel slip is corrected, a pressure increase occurs. The eBCM increases the pressure to individual wheels during deceleration in order to reduce the speed of the wheel. the isolation valve is opened and the dump valve is closed. The increased pressure is delivered from the master cylinder.
DYNAMIC REAR PROPORTIONING (DRP)
The dynamic rear proportioning (DRP) is a control system that enhances 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 electronic brake control module (EBCM). the DRP uses active control with existing ABS in order to regulate the vehicle's rear brake pressure.
Stay tuned for more when I stretch my hands... had to type this in by hand.
-Phil
. Sorry for the delay, will type up the rest shortly!
