Land Rover Discovery Owners & Service Manuals

Land Rover Discovery: Speed Control / Description and operation

Speed Control Actuator (G1347794) Removal and Installation

REMOVAL

Refer to: Accelerator Pedal (310-02 Acceleration Control, Removal and Installation).

INSTALLATION

To install, reverse the removal procedure.

Speed Control Deactivator Switch (G1661109) Removal and Installation

REMOVAL

Refer to: Stoplamp Switch (417-01 Exterior Lighting, Removal and Installation).

INSTALLATION

  1. Refer to: Stoplamp Switch (417-01 Exterior Lighting, Removal and Installation).

Speed Control Description and operation

COMPONENT LOCATION

COMPONENT LOCATION

  1. Adaptive Speed Control Module (ASCM) - only vehicle with adaptive speed control
  2. Engine Control Module (ECM)
  3. Instrument Cluster (IC)
  4. Right steering wheel switchpack

OVERVIEW

There are three variants of speed control available; a standard speed control system, an adaptive speed control system and an Automatic Speed Limiter (ASL) system.

The standard speed control system maintains a set speed selected by the driver until operation is suspended or cancelled by a further input from the driver and is controlled by the Engine Control Module (ECM).

The adaptive speed control system includes the same functionality as the standard system, and has the following additional functions:

  • Follow Mode: Automatically reduces vehicle speed, to less than the set speed, in order to maintain a selected time gap behind a slower moving vehicle, then automatically accelerate the vehicle back to the set speed, once the way ahead is clear.
  • Queue Assist: Stops the vehicle a set distance behind the vehicle in front if it comes to a halt. When the vehicle in front moves away, a brief press of the accelerator pedal resumes adaptive speed control operation.
  • Forward alert: Alert the driver when the vehicle comes within a given time gap of a slower moving vehicle.
  • Intelligent emergency braking (IEB): Applies the brakes to reduce the impact velocity if a collision is unavoidable.

The ASL system restricts the vehicle speed to an adjustable preset maximum, and will prevent the vehicle exceeding that speed.

Automatic Speed Limiter (ASL)

The ASL system is activated via an 'LIM' switch on the right steering wheel switchpack. The system speed is set using the speed control SET '+' and '-' switches. The selected speed is displayed in the instrument cluster. The set speed can be adjusted at any time using the speed control '+' or '-' switches. ASL can be suspended by pressing the 'CANCEL' switch. ASL can be resumed using the 'RESUME' switch, at any vehicle speed from stationary up to 30 km/h (19 mph) above the previously selected limit speed. If the vehicle speed is too high to resume ASL operation, a message will be displayed in the instrument cluster.

The ASL system allows full driver control of the vehicle speed up to the set speed. The speed limiter will restrict the vehicle speed and will not allow the speed to go over the set limit. If kickdown is activated (by fully depressing the accelerator pedal), ASL will be temporarily overridden.

This system operates in exclusivity with the standard speed control system and the adaptive speed control system, only one of these systems can be active at any one time.

On a vehicle fitted with the ASL system, the speed control system that was in use when the ignition was turned off (ignition mode 0) is saved and enabled again when the ignition is turned back on (ignition mode 6).

However the speed settings are not remembered and will have to be set again with the SET '+' switch.

SPEED CONTROL

The speed control systems have the following components:

  • SET '+' switch
  • '-' switch
  • RESUME switch
  • CANCEL switch

The speed control system also uses:

  • Engine Control Module (ECM)
  • Right steering wheel switchpack time gap increase and decrease control switches (adaptive speed control)
  • Brake pedal switch
  • Anti-lock Brake System (ABS) control module (adaptive speed control)
  • Accelerator Pedal Position (APP) sensor
  • Clutch pedal position sensor (manual transmission only)
  • Instrument Cluster (IC)
  • Transmission Control Switch (TCS)
  • Transmission Control Module (TCM)
  • Terrain Response switchpack (All Wheel Drive (AWD) vehicles).

ADAPTIVE SPEED CONTROL

The adaptive speed control system uses an Adaptive Speed Control Module (ASCM) to track targets ahead. When a moving target vehicle ahead is considered to be in the host vehicle's path, the adaptive speed control system will monitor the time gap between the host and the target vehicle.

When a target vehicle in front is travelling at a slower speed than the host vehicle's set speed, the host vehicle's speed will be lowered by the adaptive speed control system. The adaptive speed control system slows the host vehicle speed by requesting a slower vehicle speed from the engine and/or applying the brakes, until the correct gap between the host and target vehicle is attained. When the slower target vehicle moves into an adjacent lane or accelerates, then the host vehicle will accelerate back to the set speed. The driver can chose between four gap settings. These gaps are time gaps and not fixed distance gaps to the slower vehicle in front. When engaging the adaptive speed control or changing the time gap it will be temporarily displayed in the Instrument Cluster (IC).

The system will detect but not react to the following:

  • Vehicles in the oncoming lane
  • Stationary vehicles (the system will react to stationary objects under certain conditions)
  • Pedestrians.

To activate the adaptive speed control the vehicle speed must be at a minimum of 32 km/h (20 mph) and the maximum set speed is the minimum of the following two; 200 km/h (124 mph) and the vehicle maximum speed minus 10 km/h (6 mph). The adaptive speed control (including queue assist) will remain active down to stationary. With adaptive speed control (including queue assist) the driver can resume down to 10 km/h (6 mph). Adaptive speed control only functions when a set speed is entered in the system using the SET '+' switch on the right steering wheel switchpack. The adaptive speed control system only intervenes with the set speed when it detects a target vehicle, and then only if the minimum time gap is breached or is about to be breached.

It is important to note that the system is intended for use in limited driving situations, does not remove control and responsibility from the driver, and at all times can be quickly overridden. The adaptive speed control system is not a collision warning system and will under certain conditions not react to stationary objects.

COMPONENT DESCRIPTION

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