ABS Description and Operation Without JL7
This vehicle is equipped with the DBC 7.2 antilock braking system.
The vehicle is equipped with the following braking systems:
| • | Antilock Brake System (ABS) |
| • | Engine Drag Control (EDC) |
| • | Dynamic Rear Proportioning (DRP) |
| • | Traction Control System (TCS) |
| • | Vehicle Stability Enhancement System (VSES) (w/JL4) |
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: |
| - | Inlet valves (one per wheel) |
| - | Outlet valves (one per wheel) |
| - | Master cylinder isolation valves (one per drive wheel) |
| - | Prime valves (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--The TCS is manually disabled or enabled using the traction control switch. |
| • | Stoplamp switch--The EBCM uses the stoplamp switch as an indication that the brake pedal is applied. |
| • | Lateral accelerometer sensor (w/JL4)--The EBCM uses the lateral accelerometer sensor as an indication of the lateral acceleration of the vehicle. |
| • | Yaw rate sensor (w/JL4)--The EBCM uses the yaw rate sensor as an indication of the yaw rate of the vehicle. |
| • | Steering wheel position sensor (SWPS) (w/JL4)--The EBCM uses the SWPS as an indication of the position and rotation of the steering wheel. |
Initialization Sequence
The EBCM performs 1 initialization test each ignition cycle. The initialization of the EBCM occurs when 1 set of the following conditions occur:
Both of the following conditions occur:
| • | The EBCM detects that there is a minimum of 500 RPM from the ECM via a 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.
Engine Drag Control (EDC)
When the driver releases the throttle, and the drag from the engine overcomes the frictional force between the tire and the road, EDC becomes active.
The EBCM sends a torque request signal to the ECM, which increases the torque at the wheels. This stabilizes the wheels by reducing the slip at the driven wheels.
When EDC is active, the driven wheels are controlled to a target below the non-driven wheels.
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)
When drive wheel slip is noted while the brake is not applied, the electronic brake control module (EBCM) will enter traction control mode.
First, the EBCM requests the engine control module (ECM) to reduce the amount of torque to the drive wheels via the serial data. The ECM reduces torque to the drive wheels by retarding spark timing and turning off fuel injectors. The ECM reports the amount
torque delivered to the drive wheels via the serial data 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:
ABS Indicator
The instrument panel cluster (IPC) illuminates the Antilock Brake System (ABS) indicator when the following occurs:
| • | The electronic brake control module (EBCM) detects a malfunction with the antilock brake system. The IPC receives a serial data message from the EBCM requesting illumination. |
| • | The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 5 seconds. |
| • | The IPC detects a loss of serial data communications with the EBCM. |
Traction Control System Indicator
TRAC OFF
The instrument panel cluster (IPC) illuminates the TRAC OFF indicator when the following occurs:
| • | The electronic brake control module (EBCM) inhibits the traction control system due to a malfunction in the traction control system. The IPC receives a serial data message from the EBCM requesting illumination. |
| • | The body control module (BCM) detects that the traction control switch has been pressed (signal circuit is low). The BCM sends a serial data message to the EBCM in order to disable traction control. The IPC receives a serial data message from the
EBCM requesting illumination. The BCM sends a serial data message to the radio in order to activate an audible warning. |
Vehicle Stability Enhancement System (VSES)
The vehicle stability enhancement system (VSES) adds an additional level of vehicle control to the EBCM.
Yaw rate is the rate of rotation about the vehicle's vertical axis. The VSES is activated when the EBCM determines that the desired yaw rate does not match the actual yaw rate as measured by the yaw rate sensor.
The desired yaw rate is calculated from the following parameters:
| • | The position of the steering wheel |
| • | The speed of the vehicle |
| • | The lateral, or sideways acceleration of the vehicle |
The difference between the desired yaw rate and the actual yaw rate is the yaw rate error, which is a measurement of oversteer or understeer. If the yaw rate error becomes too large, the EBCM attempts to correct the vehicle's yaw motion by applying differential
braking to the appropriate wheel. The amount of differential braking applied to the left or right front wheel is based on both the yaw rate error and side slip rate error.
The VSES activations generally occur during aggressive driving, in turns or on bumpy roads without much use of the accelerator pedal. When braking during VSES activation, the pedal pulsations feel different than the ABS pedal pulsations. The brake pedal
pulsates at a higher frequency during VSES activation.
ABS Description and Operation With JL7
This vehicle is equipped with Active Front Steering with Enhanced StabiliTrak, and operates on a chassis CAN to communicate between the following for Active Front Steering with StabiliTrak System: Vehicle Stability Control Module (VSCM), Electronic Brake
Control Module (EBCM), MR-RTD Controller, Power Steering Control Module (PSCM), Acceleration Sensor and the Steering Position Sensor. The electronic brake control module (EBCM) is a TRW 440 V ABS/EBD/TCS/VSES brake system . The electronic brake control
module (EBCM) and the brake pressure modulator valve (BPMV) is serviced separately. The BPMV uses a 4 circuit configuration to control hydraulic pressure to each wheel independently
The vehicle is equipped with the following braking systems:
| • | Antilock Brake System (ABS) |
| • | Engine Drag Control (EDC) |
| • | Dynamic Rear Proportioning (DRP) |
| • | Traction Control System (TCS) |
| • | Active Front Steering with Enhanced StabiliTrak (w/JL7) |
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: |
| - | Inlet valves (one per wheel) |
| - | Outlet valves (one per wheel) |
| - | Master cylinder isolation valves (one per drive wheel) |
| - | Prime valves (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--The TCS is manually disabled or enabled using the traction control switch. |
| • | Stoplamp switch--The EBCM uses the stoplamp switch as an indication that the brake pedal is applied. |
| • | Lateral accelerometer sensor (w/JL7)--The EBCM uses the lateral accelerometer sensor as an indication of the lateral acceleration of the vehicle. |
| • | Yaw rate sensor (w/JL7)--The EBCM uses the yaw rate sensor as an indication of the yaw rate of the vehicle. |
| • | Steering wheel position sensor (SWPS) (w/JL7)--The EBCM uses the SWPS as an indication of the position and rotation of the steering wheel. |
Initialization Sequence
The EBCM performs 1 initialization test each ignition cycle. The initialization of the EBCM occurs when 1 set of the following conditions occur:
Both of the following conditions occur:
| • | The EBCM detects that there is a minimum of 500 RPM from the ECM via a 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.
Engine Drag Control (EDC)
When the driver releases the throttle, and the drag from the engine overcomes the frictional force between the tire and the road, EDC becomes active.
The EBCM sends a torque request signal to the ECM, which increases the torque at the wheels. This stabilizes the wheels by reducing the slip at the driven wheels.
When EDC is active, the driven wheels are controlled to a target below the non-driven wheels.
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)
When drive wheel slip is noted while the brake is not applied, the electronic brake control module (EBCM) will enter traction control mode.
First, the EBCM requests the engine control module (ECM) to reduce the amount of torque to the drive wheels via the serial data. The ECM reduces torque to the drive wheels by retarding spark timing and turning off fuel injectors. The ECM reports the amount
torque delivered to the drive wheels via the serial data 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:
Active Front Steering with StabiliTrak
· The active Front steering with stabilitrak system provides the vehicle with enhanced stability and maneuverability. Real time control of the steering and suspension subsystems contribute to enhanced stability performance over and above a brakes
only stability control system.
· Active Front steering with stabilitrak is a feature that provides integration of chassis control subsystems in order to detect and mitigate vehicle directional error. This is accomplished via a supervisor control function that uses driver inputs
and vehicle sensors to determine driver intent and vehicle directional error and provides subsystem coordination to mitigate the directional error. active Front steering with stabilitrak determines control actions that will help provide stable handling and adjust
vehicle direction toward driver intent. Real time control of the brakes, steering, suspension subsystems and powertrain torque commands are utilized to enhance vehicle stability and maneuverability. The following components are involved in the operation of the
above systems:
| • | Acceleration and Yaw Rate Sensor |
| • | Steering Angle Position Sensor |
| • | Power Steering Control Module (PSCM) |
| • | Electronic Brake Control Module (EBCM) |
| • | Wheel Speed Sensors (x4) |
| • | Master Cylinder Pressure sensor |
| • | Magneto-Rheological, Real Time Damping (MR-RTD) Module |
| • | Relative Level Sensors (x4) |
| • | Accelerator Pedal Position Sensor |
| • | Instrumentation Panel Cluster (IPC) Module |
| • | Vehicle Stability Control Module (VSCM) |
ABS Indicator
The instrument panel cluster (IPC) illuminates the Antilock Brake System (ABS) indicator when the following occurs:
| • | The electronic brake control module (EBCM) detects a malfunction with the antilock brake system. The IPC receives a serial data message from the EBCM requesting illumination. |
| • | The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 5 seconds. |
| • | The IPC detects a loss of serial data communications with the EBCM. |
Traction Control System Indicator
TRAC OFF
The instrument panel cluster (IPC) illuminates the TRAC OFF indicator when the following occurs:
| • | The electronic brake control module (EBCM) inhibits the traction control system due to a malfunction in the traction control system. The IPC receives a serial data message from the EBCM requesting illumination. |
| • | The body control module (BCM) detects that the traction control switch has been pressed (signal circuit is low). The BCM sends a serial data message to the EBCM in order to disable traction control. The IPC receives a serial data message from the
EBCM requesting illumination. The BCM sends a serial data message to the radio in order to activate an audible warning. |
SERVICE STABILITY SYS
This message displays if there has been a problem detected with the stability system. If this message comes on while driving for vehicles with the Active Front Steering with Enhanced StabiliTrak option, in some cases when the SERVICE STABILITY SYS message
is displayed, a larger degree of steering wheel input at low vehicle speeds and a smaller degree of steering wheel input at higher vehicle speeds may be required.
STABILITY SYS OFF
This message displays any time StabiliTrak or Enhanced StabiliTrak is turned off using the TC (traction control) on/off button.
When this message has been displayed, StabiliTrak or Enhanced StabiliTrak is no longer available to assist with directional control of the vehicle.
STABILITY SYS ACTIVE
This message displays any time the StabiliTrak system or Enhanced StabiliTrak system is actively assisting with directional control of the vehicle. Slippery road conditions may exist when this message is displayed, so adjust your driving accordingly. This
message may stay on for a few seconds after StabiliTrak stops assisting with directional control of the vehicle.
STABILITY SYS READY
This message displays any time StabiliTrak is turned back on using the TC (traction control) on/off button.
When this message has been displayed, StabiliTrak is ready to assist with directional control of the vehicle, if needed.
STABILITY SECURE MODE
If your All-Wheel Drive (AWD) vehicle has the Active Steering with Enhanced StabiliTrak option, this message displays when the stability control system is in the secure mode. Stability Secure Mode is set automatically when certain system faults or vehicle
conditions are detected. When the Stability Secure Mode is activated, the stability control system will not respond to driver requests to change the stability mode until the next ignition cycle or until the vehicle condition or fault is returned to normal.
STABILITY TOURING MODE
If your All-Wheel Drive (AWD) vehicle has the Active Steering with Enhanced StabiliTrak option, this message displays when the Stability Touring Mode is re-activated by using the traction control button after:
| • | Driving in the Stability Competitive Mode. |
| • | The stability control system is turned off by the driver. |
This message may also display after exiting STABILITY SECURE MODE when certain system faults or vehicle conditions have been cleared.
STABILITY COMPETITIVE MODE
If your All-Wheel Drive (AWD) vehicle has the Active Steering with Enhanced StabiliTrak option, this message displays when the Competitive Mode for stability control has been turned on using the TC (traction control) button.
When the Enhanced StabiliTrak Competitive Mode has been activated, traction control operates in competitive mode and cannot be turned off. Also, the Active Steering and the Magnetic Ride Control systems operate in the Performance Mode.
