For 1990-2009 cars

### Brake Pressure Modulator Valve (BPMV)

ABS Components
ABS/TCS Schematics

The Brake Pressure Modulator Valve (BPMV), mounted on the left 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 EBTCM, the Brake Pressure Modulator Valve (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 left rear and right front 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 motor driven recirculation pump. The pump serves two purposes: 1) During ABS pressure decrease events, it transfers fluid from the brake calipers back to the master cylinder; and 2) During traction control, it transfers fluid from the master cylinder to the rear brake calipers. The pump and motor are located within the BPMV and are not serviced separately.

#### ABS Valves

The ABS valves decrease or maintain brake fluid pressure at the individual wheel circuits. There are four inlet and four outlet solenoid valves. The solenoid valves maintain, increase, or decrease brake fluid pressure to the individual wheel circuits. The EBTCM commands the valves to their correct position during an antilock or traction event. During antilock mode, the pressure in each hydraulic circuit can be held or released by activating the appropriate valves. The normal state of the inlet valves is open, while the normal state of the outlet valves is closed. This allows direct master cylinder pressure to the brakes during normal braking. The ABS valves are located within the BPMV and are not serviced separately.

#### TCS Master Cylinder Isolation Valves

There are two TCS Master Cylinder Isolation Valves within the BPMV. These valves isolates the master cylinder so the pump motor can build brake fluid pressure for the rear brakes during a traction event.

#### TCS Prime Valves

There are two TCS Prime Valves within the BPMV. These valves allow the pump to draw fluid from the master cylinder reservoir, through the compensating ports in the master cylinder bore.

### Electronic Brake And Traction Control Module

The EBTCM performs the following primary functions:

• | Detects wheel slip tendencies

• | Detects wheel speed differences

• | Controls the brake system while in the antilock or traction control mode

• | Monitors the system for proper electrical operation

The EBTCM also controls the display of the ABS and traction control DTCs while in diagnostic mode. The EBTCM continuously checks the speed of each wheel in order to determine if any wheel is beginning to slip. If a wheel slip tendency is detected, the EBTCM commands the appropriate valve positions to modulate the brake fluid pressure in some or all of the hydraulic circuits. This action prevents wheel slip and provides optimum braking. The EBTCM continues to control pressure in the individual hydraulic circuits until a slipping tendency is no longer present. The EBTCM continuously monitors the ABS/TCS for proper operation. If an error is detected, the EBTCM can disable the ABS/TCS and turn on the ABS or TC indicators in the instrument panel.

#### Pump Motor Relay and Solenoid Valve Relay

The pump motor relay provides power to the pump motor during antilock braking and traction control. The solenoid valve relay provides power to the solenoid valves in the BPMV. Both of these relays are an integral part of the EBTCM and cannot be serviced separately.

### Wheel Speed Sensors

#### Front Wheel Speed Sensor

(1) | Steering Knuckle
(2) | Wheel Speed Sensor Bolt
(3) | Wheel Speed Sensor

#### Rear Wheel Speed Sensor

(1) | Wheel Speed Sensors
(2) | Wheel Speed Sensor Bolts
(3) | Rear Differential

A wheel speed sensor is located at each front wheel and at each rear wheel. The sensors use AC voltage in order to transmit wheel speed information to the EBTCM. Passing a toothed sensor ring past a stationary sensor causes the magnetic induction that generates the voltage. A pair of wires carry the signal to the EBTCM.

The front wheel speed sensors are located in the front steering knuckles and are not adjustable. The sensor gap is set at the time of assembly. The connectors for each wheel speed sensor are located near the wheelhouse panel. The front wheel speed sensor rings are integral with the front hubs and cannot be replaced separately.

The rear wheel speed sensors are mounted at each end of the differential housing and are not adjustable. Sensor gap is set at the time of assembly. The rear wheel speed sensor rings are integral with the rear wheel drive shafts and cannot be replaced separately.

### Traction Control System ON/OFF Switch

The Traction Control On/Off Switch (TCS Switch) is a momentary on switch located in the instrument panel that allows the driver to shut off the TCS for personal or diagnostic reasons. Turning the switch to off places the TCS in the passive mode while maintaining ABS functions. With the TCS system on, pressing the switch disables the TCS and the TC indicator turns on. If the ignition switch is turned to the OFF position then back to the RUN position, TCS resets to enable. This insures a consistent state at start up for the driver.

#### Component Location View

(1) | Hydraulic Brake Circuit
(2) | ABS/TCS Assembly
(3) | Electronic Traction Control Switch
(4) | TC Indicator
(5) | ABS Indicator
(6) | Rear Wheel Speed Sensors
(7) | Wheel Speed Sensor Harness
(8) | Front Wheel Speed Sensors