Understanding and Using Hill Descent Control (HDC)
The Hill Descent Control (HDC) system is designed to assist drivers in managing vehicle speed when descending steep inclines, particularly in off-road conditions. It works in conjunction with the anti-lock braking system (ABS) to provide controlled descents.
HDC System Overview
HDC enhances control during off-road driving, especially on downhill slopes. It can be utilized in Drive (D), Reverse (R), and CommandShift modes. When the selector is in 'D', HDC automatically selects the most appropriate gear for a controlled descent. It is not advisable to operate the vehicle with HDC engaged if the selector is in Neutral (N), unless shifting gears via the transfer case.
Note: Some Terrain Response system programs may automatically engage or disengage HDC. If HDC is manually activated, it will not be automatically disengaged by the Terrain Response system.
HDC Indicator Light
HDC can be activated at speeds below 80 km/h (50 mph), but for the system to function, the vehicle must be traveling below 50 km/h (30 mph).
When HDC conditions are met, the green HDC indicator light will illuminate steadily. For example, this occurs when the speed drops below 50 km/h (30 mph) and HDC is engaged.
If the indicator light flashes, HDC is engaged, but the conditions for its operation are not met (e.g., excessive speed), or HDC is gradually disengaging. Refer to the section on gradual HDC disengagement for more details.
If HDC is engaged and the vehicle speed exceeds 50 km/h (30 mph), HDC will enter standby mode, and the HDC indicator will flash. A corresponding message will appear on the information display.
Activating and Deactivating HDC
To activate HDC, press and release the switch (indicated by the arrow). The HDC indicator light will illuminate. To deactivate, press and release the switch again, and the indicator light will extinguish.
If HDC disengages while operating, it does so gradually, allowing the vehicle to increase speed progressively. In low-range gear, HDC can manage the vehicle at lower set speeds. For steep descents, it is recommended to use a lower gear range.
Note: HDC automatically disengages if the ignition is switched off for more than 6 hours.
HDC Operation
HDC should be used with the correct gear selected. It can be used in D (Drive), R (Reverse), and CommandShift modes. When the selector is in 'D', HDC automatically selects the most suitable gear for a controlled descent.
When descending a hill with HDC, the system maintains a set speed up to 20 km/h (12 mph). If engine braking alone is insufficient to control the vehicle's speed, HDC will automatically apply the brakes to maintain the speed corresponding to the selected gear and accelerator pedal position.
Image Description: The image shows a steering wheel control with buttons labeled 'RES', '+', and 'SET', and a button labeled '1' and '2'. Below this is a diagram illustrating the brake system, likely related to HDC engagement.
Adjusting Set Speed
While HDC is regulating the vehicle's speed, the set speed can be adjusted using the cruise control switches (+ and –) on the steering wheel.
To decrease the set speed, press and hold the '–' switch. The speed at which the switch was released becomes the new set speed.
To set a minimum speed for a selected gear, stop the vehicle using the brake pedal. Setting the minimum speed is done before releasing the brake pedal and starting the descent.
Note: Each gear has a pre-set minimum HDC speed.
To increase the set speed, press and hold the '+' switch. The speed at which the switch was released becomes the new set speed. The speed can also be adjusted incrementally by pressing the '+' or '–' switches. Each press adjusts the speed by approximately 0.5 km/h (0.3 mph).
Note: The set speed will only increase if the incline is steep enough to overcome the vehicle's momentum when braking efficiency decreases.
On gentle slopes, pressing the '+' switch may not increase the speed.
Off-Road Driving with HDC
When driving off-road, HDC can be engaged for continuous operation to maintain control. The ABS and traction control systems remain fully operational and will engage as needed.
Note: When HDC is engaged, gear changes occur normally.
If the brake pedal is pressed while HDC is active, HDC will be temporarily cancelled, and the brakes will operate normally. You may feel a series of pulses through the brake pedal. If the brake pedal is then released, HDC will resume operation at the speed at which the pedal was released.
In demanding conditions, HDC may cause brake temperatures to rise above normal limits. In such cases, an "HDC SYSTEM UNAVAILABLE COOLING" message will appear on the information display. HDC will gradually disengage and become temporarily inactive. HDC will not operate until brake temperatures return to acceptable levels. The warning message will then disappear, and HDC will resume operation as needed.
HDC System Malfunctions
If an HDC system malfunction is detected, the message "HDC SYSTEM UNAVAILABLE" will be displayed on the information panel.
If a malfunction occurs during HDC operation, the system will gradually disengage. Avoid steep descents when HDC is not functioning; use a lower gear and/or the brake pedal instead.
If a malfunction is detected, consult a Land Rover dealer or technical center as soon as possible.
Gradual HDC Disengagement
Gradual HDC disengagement allows for controlled acceleration by reducing brake pressure, enabling the vehicle's speed to be managed by engine braking alone. Following this, HDC enters standby mode.
During gradual disengagement, the HDC indicator light flashes. If necessary (e.g., the incline levels out significantly), gradual disengagement can be initiated intentionally by switching off HDC while it is operating; the indicator light will then extinguish.
