Hydraulic Control Assembly - Antilock Brakes: Description and Operation

EBTCM/BPMV:

PURPOSE
The Brake Pressure Modulator Valve (BPMV) mounted on the left front side of the engine compartment, provides brake fluid modulation for each of the individual wheel circuits as required during "Antilock" braking. During the "Antilock" mode, the BPMV can maintain or reduce brake fluid pressure independent of the pressure generated in the master cylinder. The BPMV does not provide more pressure than is applied by the master cylinder during braking. With the exception of the Electronic Brake (and Traction) Control Module (EBCM/EBTCM), the BPMV is an integral, non-serviceable component. The BPMV should never be disassembled. The BPMV uses a four circuit configuration with a diagonal split. Individual circuits are provided for the left front and right rear wheels, and right front and left rear wheels. The diagonal circuits are hydraulically isolated so that a leak or malfunction in one circuit will allow continued braking ability on the other. The BPMV consists of several other components which are described as follows:

PUMP MOTOR
The BPMV contains a pump which circulates brake fluid back to the master cylinder during the pressure release mode of the "Antilock" brake. The pump also supplies hydraulic fluid pressure during "Traction Control." The pump is located in the Brake Pressure Modulator Valve and cannot be serviced separately.

SOLENOID VALVES
If the vehicle is equipped with "Traction Control" then the BPMV has 12 solenoid valves. If the vehicle is not equipped with "Traction Control" then the BPMV has 8 solenoid valves, and they are not serviceable. There are four Hold, four Release, two Traction Control System (TCS) isolating, and two TCS prime solenoid valves. The solenoid valves maintain, increase, or decrease brake fluid pressure to the individual wheel circuits. The EBCM/EBTCM commands the valves to their correct position during "Antilock" or "Traction Control" braking.