Part 1

Anti-Lock Control - Stability Assist

COMPONENT LOCATION

NOTE:
Left-Hand Drive (LHD) shown; Right-Hand Drive (RHD) similar.









OVERVIEW
The vehicle ABS and stability control system features a Continental Teves Mk25E1 module, with an integral 4-channel HCU. The integrated ABS module and HCU is located on the rear LH side of the engine compartment, and is installed in the brake hydraulic circuit between the brake master cylinder and the 4 brake calipers.
The ABS module is connected to the high speed Controller Area Network (CAN) bus, and actively interacts with other vehicle system control modules and associated sensors to receive and transmit current vehicle operating information.
When required, the ABS module will actively intervene and operate the HCU during braking or vehicle maneuvers to correct the vehicle attitude, stability, traction or speed. During severe incidents of vehicle correction, the ABS module will also request the Engine Control Module (ECM) to reduce engine power in order to further stabilize and correct the vehicle.
To provide full system functionality, the ABS and DSC systems comprise the following components:
- DSC switch
- HDC switch
- 4 wheel speed sensors
- Sensor cluster
- Steering angle sensor
- Instrument cluster indicator lamps
- Integrated ABS module and HCU.
The ABS system also provides brake functions that are designed to assist the vehicle or aid the driver. The following functions are detailed in the section 'Principles of Operation':
- Anti-lock Brake System (ABS)
- Corner Brake Control (CBC)
- Dynamic Stability Control (DSC)
- Electronic Brake Force Distribution (EBD)
- Electronic Traction Control (ETC)
- Emergency Brake Assist (EBA)
- Engine Drag-Torque Control (EDC)
- HDC (with gradient release control)
- Roll Stability Control (RSC)
- Terrain Response system integration.
All the brake functions listed, apart from HDC, are automatically active when the ignition is in power mode 6 (ignition) and the engine is running.

DYNAMIC STABILITY CONTROL SWITCH
The DSC switch allows the DSC function to be selected off. The DSC switch is non-latching and is installed in the floor console, forward of the gear selector lever. Pressing the DSC switch connects an ignition power feed to the ABS module. With the first press of the DSC switch, the ABS module disables the DSC functions. When the DSC switch is pressed again, the ABS module re-enables the DSC functions. The DSC switch must be pressed for a minimum of 0.3 second for the ABS module to react. The DSC function is re-enabled at the beginning of each ignition cycle.
To confirm that the DSC function is selected off, the amber colored DSC warning indicator lamp located in the instrument cluster, is continuously illuminated. On vehicles installed with a high-line instrument cluster, a message is also displayed in the message center to confirm that DSC is selected off.
For additional information, refer to Instrument Cluster Initial Inspection and Diagnostic Overview
For additional information, refer to Information and Message Center Description and Operation
When the DSC function is selected on, the DSC warning indicator lamp is extinguished.
Although Land Rover recommend that DSC is selected on for all normal driving conditions, it may be beneficial to de-select DSC in order to maximize traction under the following conditions:
- To rock the vehicle out of a hollow or a soft surface.
- When driving on loose surfaces or with snow chains installed.
- When driving in deep sand, snow or mud.
- When driving on tracks with deep longitudinal ruts.
Even when DSC is deselected, driving maneuvers with extreme yaw or lateral acceleration may trigger RSC activity to assist the vehicle stability.
To prevent mis-use of, or in the event of a broken DSC switch, a Diagnostic Trouble Code (DTC) is stored in the ABS module memory if the input from the DSC switch is held high for more than 1 minute.

HILL DESCENT CONTROL SWITCH
The HDC switch controls the selection of the HDC function.
The HDC switch is non-latching and is installed in the floor console, forward of the gear selector lever. Momentarily pressing and releasing the HDC switch connects an ignition power feed to the ABS module. With the first press and release of the HDC switch, the ABS module enables operation of the HDC function. When the HDC switch is pressed and released again, the ABS module disables operation of the HDC function.
To prevent mis-use of, or in the event of a broken HDC switch, if the switch is pressed for more than 10 seconds no change of state occurs. A DTC is stored in the ABS module memory if the input from the HDC switch is held high for more than 1 minute.

HDC Activating Stoplamps
Operation of the vehicle stoplamps during HDC is controlled by the CJB. The ABS module monitors the brake system hydraulic pressure and requests the CJB, via the high speed CAN bus, to energize the stoplamps during active braking.
A pressure threshold and time filter prevents the stoplamps from flickering while HDC is braking.

Stop/Start Vehicles - From 2010 MY
Activation of Hill Descent Control will deactivate the Stop/Start system. However, if Hill Descent Control is activated when the engine is shutdown in a Stop/Start cycle the engine will automatically restart. If during this event the Stop/Start system cannot detect the driver's occupancy, for example either the driver's safety belt or door is unlatched, the engine will not restart. The Stop/Start system will request the driver to depress the clutch to restart the engine. The driver will be informed of this by 'RESTART REQUIRED PRESS CLUTCH' being displayed in the message center.
The driver must respond to this request within a limited time period, or otherwise a conventional engine restart using the ignition switch will be required. For additional information, refer to Starting System

WHEEL SPEED SENSORS









An active wheel speed sensor is installed in each wheel knuckle, and provides the ABS module with a rotational speed signal from each road wheel. The head of each wheel speed sensor is positioned close to a magnetic encoder incorporated into the seal of the wheel bearing. Each front axle bearing encoder contains 44 north and south poles; each rear axle bearing encoder contains 48 pole pairs. A fly lead connects each sensor to the vehicle harness.
The wheel speed sensor is supplied with a power supply and a signal connection from the ABS module. When the ignition switch is in power mode 6 (ignition), the ABS module supplies power to the wheel speed sensors and monitors the return signals. Rotation of the wheels induces current fluctuations in the speed sensor return signals. The ABS module subsequently converts the return signals into individual wheel speeds, and the overall vehicle speed.
The ABS module outputs the individual wheel speeds, and vehicle speed on the high speed CAN bus for use by other systems. The quality of the vehicle speed signal is also broadcast on the high speed CAN bus. If all wheel speed signals are available to calculate vehicle speed from, the quality of the vehicle speed signal is set to 'data calculated within specified accuracy'. If one or more wheel speed sensors are inoperative, the quality of the vehicle speed signal is set to 'accuracy outside specification'.
The ABS module monitors the wheel speed sensor circuits for faults. If a fault is detected the ABS module stores a related DTC in memory and illuminates the appropriate warning indicator lamps, depending on the system functions affected (DSC/ETC, ABS, EBA/EBD, HDC). A warning chime is also sounded to alert the driver to the fault condition.
For vehicles installed with a high-line instrument cluster, a message is displayed in the message center, only if the fault affects the HDC function.
For additional information, refer to Instrument Cluster Initial Inspection and Diagnostic Overview
For additional information, refer to Information and Message Center Description and Operation
As the wheel speed sensors are active devices, a return signal is available when the road wheels are not rotating. This enables the ABS module to check the condition of the speed sensors while the vehicle is stationary.

SENSOR CLUSTER









The sensor cluster is installed beneath the center console and is secured to the transmission tunnel with 2 studs and nuts. The sensor cluster is a compact unit that provides the ABS module with inputs of yaw rate, roll rate, longitudinal and lateral acceleration. The ABS module broadcasts the input values on the high speed CAN bus for use by other systems.
When the ignition is in power mode 6 (ignition), the sensor cluster receives an ignition power feed from the ABS module. The sensor cluster is also connected to the ABS module via a private CAN bus.
The sensor cluster is diagnosed by the ABS module. If a sensor fault is detected the ABS module stores a related DTC in memory and illuminates the appropriate warning indicator lamps, depending on the system functions affected (DSC/ETC, ABS, EBA/EBD, HDC). A warning chime is also sounded to alert the driver to the fault condition.
For vehicles installed with a high-line instrument cluster, a message is displayed in the message center, only if the fault affects the HDC function.
For additional information, refer to Instrument Cluster Initial Inspection and Diagnostic Overview
For additional information, refer to Information and Message Center Description and Operation

STEERING WHEEL MODULE









The steering wheel module contains the steering angle sensor, clockspring and steering column multifunction switches to form an integral component. The steering angle sensor is connected directly to the clockspring.
The steering wheel module is mounted to the upper steering column with 2 screws, and receives an electrical supply from the main harness via a 4-pin connector located on the side of the unit. The module provides the location and electrical connection for the 2 multifunction switches.
Input signals from the steering angle sensor are received and processed by the steering wheel module to calculate the steering wheel angle, and steering wheel angle speed. The information is transmitted on the high speed CAN bus for use by the ABS module.

Steering Angle Sensor
The steering angle sensor is connected to the steering wheel with 2 dowels. The steering angle sensor monitors steering wheel rotation, and provides information of the steering wheel angle and rate of speed of steering wheel movements.
A code wheel and 16 optical digital sensors are installed inside the steering wheel angle sensor. Rotation of the code wheel is read by the optical-digital sensors to produce steering wheel rotational speed signals. The steering angle sensor is able to measure a rotation range of +/- 720 degrees, although the steering mechanism will only allow the steering wheel to rotate a maximum of +/-540 degrees.
Signals from the steering angle sensor are transmitted on the vehicle high speed CAN bus, and received and processed by other systems such as DSC. The transmitted information includes details of steering wheel angle and steering wheel rotational speed, along with signal integrity information.
If a fault occurs within the steering angle sensor, a DTC will be set and stored in the steering angle sensor memory. The steering angle sensor fault is also stored in the ABS module memory that illuminates the appropriate warning indicator lamps, depending on the system functions affected (DSC/ETC, ABS, EBA/EBD, HDC). A warning chime is also sounded to alert the driver to the fault condition.
For vehicles installed with a high-line instrument cluster, a message is displayed in the message center, only if the fault affects the HDC function.
For additional information, refer to Instrument Cluster Initial Inspection and Diagnostic Overview
For additional information, refer to Information and Message Center Description and Operation
The steering angle sensor and ABS module are able to be interrogated using the Land Rover approved diagnostic equipment.

Clockspring
The clockspring is a rotary coupling that provides the electrical connection between the fixed steering wheel module, and the steering wheel mounted controls and Supplemental Restraint System (SRS) driver's airbag.
A colored indicator is provided within the clockspring and is visible through a transparent perspex cover when the steering wheel is removed, and the steering angle sensor is aligned to the central position. The indicator makes sure the steering angle sensor and steering system are correctly aligned following repairs to the steering mechanism.

Service Information
Before separating the steering components from the connecting steering column, the clockspring must be aligned to the center position (indicator visible) and the wheels pointing straight ahead. The clockspring is retained in the central position with a locking screw.

INSTRUMENT CLUSTER INDICATOR LAMPS









The instrument cluster contains 2 types of indicator lamps to display the operating status of the selected anti-lock control - stability assist functions. The indicator lamps provide a visual notification of either a system warning or information indication to the driver. There are 4 indicator lamps on vehicles with a high-line instrument cluster; 5 indicator lamps on vehicles with a low-line instrument cluster.
The following anti-lock control - stability assist indicator lamps are installed in the instrument cluster:
- ABS warning indicator lamp
- Brake warning indicator lamp
- DSC warning indicator lamp
- HDC warning indicator lamp
- HDC information indicator lamp.
For additional information, refer to Instrument Cluster Initial Inspection and Diagnostic Overview

ANTI-LOCK BRAKE SYSTEM MODULE
The ABS module controls the brake functions by operating the HCU to modulate hydraulic pressure to the individual wheel brakes.
The ABS module is attached to the HCU and forms an integral component. A 47-pin connector provides the electrical interface between the ABS module and the vehicle wiring. The ABS module may be interrogated using the Land Rover approved diagnostic equipment.

HYDRAULIC CONTROL UNIT
The HCU is a 4 channel unit that modulates the supply of hydraulic pressure to the brakes, under the control of the ABS module.
The master cylinder primary and secondary circuit outlets are connected to the HCU primary and secondary circuits. For additional information, refer to Hydraulic Brake Actuation Description and Operation Each of the HCU circuits contains the following components to control the supply of hydraulic pressure to the brakes:
- A normally open, solenoid-operated pilot valve, to enable active braking.
- A normally closed, solenoid-operated priming valve, to connect the brake fluid reservoir to the dual circuit hydraulic pump during active braking.
- A hydraulic pump, to generate hydraulic pressure for active braking and return brake fluid to the reservoir.
- Normally open, solenoid-operated inlet valves and normally closed, solenoid-operated outlet valves, to modulate the hydraulic pressure in the individual brakes.
- An accumulator and a relief valve, to allow the fast release of pressure from the brakes.
- Filters, to protect the internal components from contamination.
The primary circuit also incorporates a pressure sensor to provide the ABS module with a hydraulic pressure signal.
Contact pins on the HCU mate with contacts on the ABS module to provide the electrical connections from the ABS module to the dual circuit hydraulic pump motor, and the pressure sensor. The solenoids that operate the valves are installed within the ABS module.