SRX AWD V8-4.6L VIN A (2004)
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 Electronic Brake Control Module (EBCM) detects a malfunction with the antilock brake system. The IPC receives a class 2 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 class 2 communications with the EBCM.
Traction Control System Indicator
TRAC OFF
The 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 class 2 message from the EBCM requesting illumination.
^
The rear integration module (RIM) detects that the traction control switch has been pressed (signal circuit is low). The RIM sends a class 2
message to the EBCM in order to disable traction control. The IPC receives a class 2 message from the EBCM requesting illumination. The RIM
sends a class 2 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.
