center console BMW X5 2004 E53 DSC System Workshop Manual

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DSC NEW FUNCTIONS
HILL DECENT CONTROL (HDC)
Hill Decent Control (HDC) is designed for off road use to automatically slow the vehicle and
maintain a steady speed on steep gradients. This function allows the driver to focus on
steering and controlling the vehicle without having to use the brakes to slow the vehicle.
HDC is activated manually through the push button switch located in the center switch
panel located in the console. When activated, the vehicle’s speed is held to approximately
5 MPH by the DSC system pulsing the brakes to maintain the speed.
The following conditions must be met before the HDC will activate:
• Push button pressed - LED “ON”
• Vehicle speed: < 25 MPH
• Accelerator pedal pressed <15%
• Downhill driving recognized
Downhill is recognized from the vehicle’s speed and engine load from the engine control
module. The accelerator pedal and engine load signals are passed over the CAN bus to the
DSC control module.
The HDC switch can be pressed at speeds < 37MPH and the LED will come on to indicate
standby mode. However the system will not activate until the vehicle’s speed is below 25.
The driver can accelerate with HDC active up to approximately 20% engine load. The HDC
will stop regulating as long as the driver is requesting a speed increase. If the vehicle’s
speed is > 37 MPH, the HDC function is automatically switched OFF.

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ROTATION RATE/TRANSVERSE ACCELERATION SENSOR
Located under the center console behind the MRS III control module, the rotation rate and
transverse acceleration sensor provides two inputs to the DSC control module. The sensor
is isolated from body/chassis vibrations through its rubber mounting.
For rotational speed, the sensor produces a reference signal of 2.5 volts and a linear volt-
age signal from 0.7 to 4.3 volts. This linear voltage input signal is used by the DSC control
module as the degree of rotational rate (yaw).
The sensor also produces a linear voltage signal for the lateral acceleration (G-force) that
ranges from 0.5 to 4.5 volts. The DSC control module uses this input to determine the side
forces acting on the vehicle for DSC regulation.