ABS Description and Operation
This vehicle is equipped with a TRW EBC450 brake system. The electronic brake control module (EBCM) and the brake pressure modulator valve assembly are serviced separately. The brake pressure modulator valve assembly uses a 4 circuit configuration to control hydraulic pressure to each wheel independently.
Depending on options, the following vehicle performance enhancement systems are provided.
- Antilock brake system (ABS)
- Acceleration Slip Regulation
- Stability control
- Dynamic rear proportioning
- Hill start assist
- Cornering brake control
- Hydraulic brake assist
- Trailer stability assist
The following components are involved in the operation of the above systems
- EBCM - The EBCM controls the system functions and detects failures. It supplies voltage to the solenoid valves and pump motor.
- Brake pressure modulator valve assembly - The brake pressure modulator valve assembly contains the following components: Hydraulic pump with pump motor Four isolation vales Four dump valves Two traction control/stability control supply valves Two traction control/stability control isolation valves Pressure Sensor High pressure attenuators Low pressure accumulator
- Multi-axis acceleration sensor - The yaw rate, lateral acceleration and longitudinal acceleration sensors are combined into one multi-axis acceleration sensor, external to the EBCM. The EBCM receives serial data message inputs from the yaw rate, lateral acceleration and longitudinal acceleration sensor and activates stability control and hill start assist function depending on multi-axis acceleration sensor input.
- Steering angle sensor - The EBCM receives serial data message inputs from the steering angle sensor. The steering angle sensor signal is used to calculate the desired yaw rate.
- Traction control switch - Traction control and stability control are manually disabled or enabled by pressing the traction control switch.
- Wheel speed sensors - The EBCM supplies a 12 V reference voltage to each wheel speed sensor. As the wheel spins, the wheel speed sensor produces an alternating current square wave signal. The EBCM uses the frequency of the square wave signal to calculate the wheel speed.
Circuit/System Description
The wheel speeds are detected by active wheel speed sensors. Each wheel speed sensor receives a 12 V reference voltage from the electronic brake control module (EBCM) and provides an alternating current square wave signal to the EBCM. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the wheel speed. The EBCM sends the wheel speed information as a high speed controller area network (CAN) serial data message. Some modules connected to the high speed CAN bus monitor for the wheel speed information. The DTC is set when the wheel speed information has not been received.
Description and Operation
ABS DESCRIPTION AND OPERATION
The body control module (BCM) monitors the traction control switch. When the traction control switch is pressed once, the BCM will request the electronic brake control module (EBCM) via serial data to disable the traction control. When the traction control switch is pressed for 5 s, the BCM will request the EBCM to disable the stability control. The EBCM will request the instrument cluster via serial data to turn the traction control off and stability control off indicator ON to notify the driver of the deactivation.
ABS DESCRIPTION AND OPERATION
The wheel speeds are detected by active wheel speed sensors and encoder rings. The encoder ring consists of permanent magnets. Each wheel speed sensor receives a 12 V reference voltage from the electronic brake control module (EBCM) and provides an alternating current square wave signal to the EBCM. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the wheel speed.
ABS DESCRIPTION AND OPERATION
The pump motor is an integral part of the brake pressure modulator valve assembly, while the pump motor relay is integral to the electronic brake control module (EBCM). The pump motor relay is not engaged during normal system operation. When the ABS, traction control or stability control operation is required, the EBCM activates the pump motor relay and turns the pump motor ON.
ABS DESCRIPTION AND OPERATION
The brake pressure sensor is integral to the brake pressure modulator valve assembly. The electronic brake control module (EBCM) monitors the brake pressure sensor supply voltage and the signal voltage. The body control module (BCM) sends a serial data message when the brake pedal is applied.
ABS DESCRIPTION AND OPERATION
The body control module (BCM) monitors the brake pedal position sensor and sends a serial data message when the brake pedal is applied. When the vehicle is stopping, the electronic brake control module (EBCM) monitors for the brake pedal applied serial data message from the BCM, with the brake pressure increasing and the vehicle slowing down, or when the vehicle is accelerating, the brake pedal is not applied and brake pressure is not increasing.
ABS DESCRIPTION AND OPERATION
The yaw rate, lateral acceleration and longitudinal acceleration sensors are combined into one multi-axis acceleration sensor, external to the electronic brake control module (EBCM). The EBCM supplies a 12 V reference voltage to the multi-axis acceleration sensor. The multi-axis acceleration sensor communicates with the EBCM via the high speed controller area network (CAN) serial data circuit. The EBCM activates the stability control function depending on multi-axis acceleration sensor input.
ABS DESCRIPTION AND OPERATION
When traction control is active, the electronic brake control module (EBCM) sends a serial data message to the engine control module (ECM) requesting torque reduction. When certain ECM DTCs are set, the ECM will not be able to perform the torque reduction for traction control. A serial data message is sent to the EBCM indicating that traction control is not allowed.
ABS DESCRIPTION AND OPERATION
The wheel speeds are detected by active wheel speed sensors. Each wheel speed sensor receives a 12 V reference voltage from the electronic brake control module (EBCM) and provides an alternating current square wave signal to the EBCM. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the wheel speed.
ABS DESCRIPTION AND OPERATION
The yaw rate, lateral acceleration and longitudinal acceleration sensors are combined into one multi-axis acceleration sensor, external to the electronic brake control module (EBCM). The EBCM controls the stability control by monitoring the inputs of the yaw rate sensor, lateral acceleration sensor, and steering angle sensor. The readings are compared to an internal calibrated value so it knows if the vehicle is having an instability condition to activate the stability control.
ABS DESCRIPTION AND OPERATION
The brake fluid level switch monitors the fluid level in the brake fluid reservoir. When the EBCM registers that the brake fluid level switch is open, a DTC is set.
HYDRAULIC BRAKE SYSTEM DESCRIPTION AND OPERATION
The solenoid valves are integral parts of the brake pressure modulator valve assembly. The brake pressure modulator valve assembly contains an isolation solenoid valve and a dump solenoid valve for each wheel and a traction control/stability control supply solenoid valve and isolation solenoid valve for each brake circuit. The solenoid valves are not engaged during normal system operation. When the ABS, traction control or stability control operation is required the electronic brake control module (EBCM) turns the required solenoid valves ON.
ABS DESCRIPTION AND OPERATION
The vacuum sensor in the brake servo monitors the brake servo pressure. The electronic brake control module (EBCM) supplies a 5 V reference circuit and a low reference circuit to the brake servo vacuum sensor. The vacuum sensor delivers a voltage signal to the EBCM that corresponds to the pressure in the brake servo.
BRAKE ASSIST SYSTEM DESCRIPTION AND OPERATION
The steering angle sensor receives a 12 V reference voltage from the electronic brake control module (EBCM). The EBCM receives high speed controller area network (CAN) message inputs from the steering angle sensor identifying the position and direction of the steering wheel rotation. The EBCM utilizes this signal to calculate the driver intended driving direction.
ABS DESCRIPTION AND OPERATION
The electronic brake control module (EBCM) receives controller area network (CAN) serial data messages from other modules. The EBCM must be configured with the vehicle identification number (VIN), CAN configuration data and vehicle options. If not properly configured after installation, the EBCM may set a DTC.
The internal fault detection is handled inside the control module. No external circuits are involved.
ABS DESCRIPTION AND OPERATION
The electronic brake control module (EBCM) receives controller area network (CAN) serial data messages from other modules. The EBCM must be configured with the vehicle identification number (VIN), CAN configuration data and vehicle options. If not properly configured after installation, the EBCM may set a DTC.
The internal fault detection is handled inside the control module. No external circuits are involved.
ABS DESCRIPTION AND OPERATION
The vacuum sensor in the brake servo monitors the brake servo pressure. The electronic brake control module (EBCM) supplies a 5 V reference circuit and a low reference circuit to the brake servo vacuum sensor. The vacuum sensor delivers a voltage signal to the EBCM that corresponds to the pressure in the brake servo.
BRAKE ASSIST SYSTEM DESCRIPTION AND OPERATION
The wheel speeds are detected by active wheel speed sensors. Each wheel speed sensor receives a 12 V reference voltage from the electronic brake control module (EBCM) and provides an alternating current square wave signal to the EBCM. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the wheel speed. The EBCM sends the wheel speed information as a high speed controller area network (CAN) serial data message.
ABS DESCRIPTION AND OPERATION
When the ignition is turned ON, the microprocessor runs a diagnostic program to detect an internal fault when power up is commanded. If an internal malfunction is detected, the control module will set a DTC.
ABS DESCRIPTION AND OPERATION
The instrument cluster illuminates the traction control/stability control-active indicator, traction control off indicator and stability control off indicator for 5 s after ignition ON. The electronic brake control module (EBCM) will request the instrument cluster via serial data to turn the traction control/stability control-active indicator ON (flashing) when the system is in traction control or stability control mode. When the EBCM detects a fault it sends a serial data message to the instrument cluster commanding the traction control/stability control-active indicator ON.
The body control module (BCM) monitors the traction control switch. When the traction control switch is pressed once, the BCM will request the EBCM via serial data to disable the traction control. When the traction control switch is pressed for 5 s, the BCM will request the EBCM to disable the stability control. The EBCM will request the instrument cluster via serial data to turn the traction control off and stability control off indicator ON to notify the driver of the deactivation.
ABS DESCRIPTION AND OPERATION
The instrument cluster turns ON the ABS indicator for 5 s after ignition ON or when the electronic brake control module (EBCM) detects a fault and sends a serial data message to the instrument cluster commanding the indicator ON.
ABS DESCRIPTION AND OPERATION