BMW X5: HDC Hill Descent Control

Principle

HDC Hill Descent Control is a downhill control feature that controls the vehicle speed on steep downhill grades, for instance when driving on unpaved roads.

General information

When the system is active, the vehicle moves at the speed set by the driver, without the driver having to depress the brake pedal.

While HDC is controlling the speed, the system automatically distributes the braking force to the individual wheels. This improves vehicle drivability and driving stability. If necessary, the Antilock Braking System prevents the wheels from locking.

Hill Descent Control can be activated at speeds below approx. 25 mph/40 km/h.

Speeds can be set between approx. 2 mph/3 km/h and approx. 20 mph/30 km/h.

When the vehicle is driving downhill, the system reduces the speed to the set value, within the physical limits.

Overview

Button in the vehicle

HDC

Activating HDC

Press the button.

The LED on the button lights up.

Speeds between approx. 2 mph/3 km/h and approx. 20 mph/30 km/h are adopted as the set speed.

Emergency braking function, Active PDC: the emergency braking function is deactivated.

Additional information: Emergency brake function.

Display in the instrument cluster

An icon and the selected desired speed are displayed.

• Indicator green: HDC is active.

  The system is actively braking the vehicle.

• Gray display: HDC is on standby.

Display in the Head-up Display

The HDC status can also be displayed in the Head-up Display.

Increasing or decreasing vehicle speed

Using the cruise control rocker switch

The set speed can be changed using the cruise control rocker switch on the steering wheel.

• Press the rocker switch up: the speed increases gradually.
• Press the rocker switch up and hold: the speed increases while the rocker switch is pressed.
• Press the rocker switch down: the speed decreases gradually.
• Press the rocker switch down and hold: the speed decreases while the rocker switch is pressed.

Using the brake pedal

While HDC is controlling the speed, the set speed can be reduced by depressing the brake pedal.

Deactivating HDC

Press the button again.

The LED goes out.

HDC is automatically deactivated above approx. 25 mph/40 km/h.

Malfunction

If a malfunction occurs, a message is displayed in the instrument cluster.

Integral Active Steering

Principle

The Integral Active Steering increases the maneuverability and makes a more direct steering response possible.

General information

Integral Active Steering is a combination of variable steering ratio and rear axle steering.

The steering is more direct because the variable steering ratio amplifies the wheel angle while maneuvering. The rear axle steering acts to increase maneuverability at low speeds by turning the rear wheels slightly in the opposite direction to the front wheels.

At higher speeds, the rear wheels are turned in the same direction as the front wheels. For instance, this results in a harmonious lane change.

In critical driving situations, the Integral Active Steering can stabilize the vehicle through purposeful steering of the rear wheels before the driver intervenes, for instance in case of over-steering.

Tuning

The system offers several different tunings.

The different tunings are assigned to the different driving modes of the Driving Dynamics Control.

Additional information: Driving Dynamics Control.

Using tire chains

In order to guarantee free movement of the wheels when operating with tire chains, rear axle steering of the integral active steering must be switched off when tire chains are mounted.

Additional information: Rear axle steering during operation with tire chains.

Malfunction

In the event of a malfunction, the steering wheel must be turned further at lower speeds, while the vehicle responds more sensitively to steering wheel movements in the higher speed range.

The stability-enhancing intervention may be deactivated.

Proceed cautiously and drive defensively.

Have the system checked by a dealer's service center or another qualified service center or repair shop.

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