For 1990-2009 cars

#### BPMV and EBCM

#### BPMV Hydraulic Flow

(1) | Master Cylinder
(2) | Master Cylinder Reservoir
(3) | Pump
(4) | Left Front Master Cylinder Isolation Valve
(5) | Left Front Prime Valve
(6) | Brake Pressure Modulator Valve (BPMV)
(7) | Damper
(8) | Right Rear Inlet Valve
(9) | Accumulator
(10) | Right Rear Brake
(11) | Right Rear Outlet Valve
(12) | Left Front Outlet Valve
(13) | Left Front Brake
(14) | Left Front Inlet Valve
(15) | Left Rear Inlet Valve
(16) | Left Rear Brake
(17) | Left Rear Outlet Valve
(18) | Right Front Brake
(19) | Right Front Outlet Valve
(20) | Accumulator
(21) | Right Front Inlet Valve
(22) | Damper
(23) | Right Front Master Cylinder Isolation Valve
(24) | Right Front Prime Valve

This vehicle is equipped with the Bosch 5.3 antilock braking system.

The vehicle is equipped with the following braking systems:

• | Antilock Brake System (ABS)

• | Dynamic Rear Proportioning (DRP)

• | Traction Control System (TCS) (w/NW9)

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 energized when the ignition is ON and no ABS DTCs are present. It supplies battery positive voltage to the solenoid valves and pump motor.

- | Vent Tube - The vent tube, located in the EBCM connector, is an opening to the internal cavity of the EBCM. It allows ventilation of the EBCM internals.

• | Brake Pressure Modulator Valve (BPMV) - The BPMV contains the hydraulic valves and pump motor that are controlled electrically by the EBCM. The BPMV uses a 4 circuit configuration with a diagonal split. The BPMV directs fluid from the reservoir of the master cylinder to the left front and right rear wheels and fluid from the other reservoir to the 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.

| Important: There is a rubber isolator located under the BPMV and on the mounting studs. The rubber isolators protect the BPMV and the EBCM from vehicle vibrations.

• | The BPMV contains the following components:

- | Pump Motor

- | Inlet Valves (one per wheel)

- | Outlet Valves (one per wheel)

- | Master Cylinder Isolation Valves (w/NW9) (one per drive wheel)

- | Prime Valves (w/NW9) (one per drive wheel)

• | Wheel Speed Sensors (WSS) - As the wheel spins, the wheel speed sensor produces an AC signal. The EBCM uses this AC signal to calculate wheel speed. The wheel speed sensors are replaceable only as part of the wheel hub and bearing assemblies.

• | Traction Control Switch (w/NW9) - The TCS is manually disabled or enabled using the traction control switch.

• | Stoplamp Switch - The EBCM uses the stop lamp switch as an indication that the brake pedal is applied.

### Initialization Sequence

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:

• | The EBCM receives that there is a minimum of 500 rpm from the PCM via class 2 serial data message.

• | The stop lamp switch is not applied.

OR

Both of the following conditions occur:

• | The vehicle speed is greater than 16 km/h (10 mph).

• | The stop lamp switch is applied.

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.

### Antilock Brake System

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.

### Pressure Hold

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.

### Pressure 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.

### Pressure Increase

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.

### Dynamic Rear Proportioning (DRP)

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 System (TCS) (NW9)

When drive wheel slip is noted while the brake is not applied, the EBCM will enter traction control mode.

First, the EBCM requests the PCM to reduce the amount of torque to the drive wheels via the requested torque signal circuit. The PCM reduces torque to the drive wheels by retarding spark timing and turning off fuel injectors. The PCM reports the amount torque delivered to the drive wheels via the delivered torque signal circuit.

If the engine torque reduction does not eliminate drive wheel slip, the EBCM will actively apply the drive wheel brakes. During traction control braking, hydraulic pressure in each drive wheel circuit is controlled to prevent the drive wheels from slipping. The master cylinder isolation valve closes in order to isolate the master cylinder from the rest of the hydraulic system. The prime valve then opens in order to allow the pump to accumulate brake fluid in order to build hydraulic pressure for braking. The drive wheel inlet and outlet solenoid valves then open and close in order to perform the following functions:

• | Pressure hold

• | Pressure increase

• | Pressure decrease

### ABS Indicator

The IPC illuminates the ABS indicator when the following occurs:

• | The IPC detects a malfunction with the antilock brake system.

• | The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

### Brake Pad Wear Indicator

The IPC illuminates the brake pad wear indicator when the following occurs:

• | The IPC detects a hardwire input from the LH or RH disc brake pad wear sensor (signal is low).

• | The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

### Brake System Indicator

The IPC illuminates the brake indicator when the following occurs:

• | The IPC detects a low brake fluid condition. The IPC receives a discrete input from the brake fluid level switch requesting illumination.

• | The IPC detects the park brake is engaged. The IPC receives a discrete input from the park brake switch requesting illumination.

• | The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

### Traction Control Indicator

The IPC illuminates the traction control indicator when the following occurs:

• | The electronic brake control module (EBCM) detects a malfunction in the traction control system. The IPC receives a hardwire input (signal is low) from the EBCM requesting illumination.

• | The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.