Part 1
Vehicle Dynamic SuspensionAIR SUSPENSION COMPONENT LOCATION
GENERAL
The air suspension system is a four corner system which is fitted to all models.
The system is electronically controlled by an air suspension control module which controls the air supply unit, reacts to inputs from four height sensors and distributes air around the system via valve blocks.
The main air suspension system components are:
^ Air suspension control module
^ Air supply unit
^ Four height sensors
^ Three valve block assemblies
^ Reservoir
^ Air harness
^ Two front struts incorporating air spring damper modules
^ Two rear air spring modules.
The four corner air suspension system maintains the vehicle height under all operating conditions by controlling the mass of air in the air springs. The air suspension control module uses signals from the four height sensors to maintain the correct suspension height, irrespective of vehicle load. Additionally, the system allows the driver to request ride height changes to improve off-road performance or ease access or loading. The system automatically adjusts the ride height to improve the vehicle handling and dynamics when speed increases or decreases. This is achieved by operating pneumatic control valves to increase or decrease the mass of air in the air springs.
The air suspension system has three driver selectable, pre-determined ride heights and an automated high speed ride height. A driver interface indicates the selected ride height and height change movement. Additional information is also relayed to the driver via the instrument cluster message center and by audible warnings also transmitted by the instrument cluster.
Most height changes can only be made when the engine is running and the driver's and passenger doors are closed.
The air suspension can be controlled manually by the driver using either a switch on the floor console or a switch on the door to select the required height change.
The system will temporarily inhibit height adjustments when the vehicle is subject to cornering, heavy acceleration or heavy braking. The inhibit function prevents unsettling of the vehicle by reducing the effective spring rates.
Height changes are also restricted for safety reasons, when a door is opened and the vehicle is stationary for example.
The air suspension system fitted to Range Rover is controlled by the air suspension control module which is located behind the passenger side of the instrument panel. The control module is housed in a plastic bracket adjacent the 'A' pillar. The control module monitors the height of each corner of the vehicle via four height sensors, which are mounted inboard of each road wheel. The control module also performs an 'on-board diagnostic' function to perform 'health checks' on the system. If faults are detected, codes are stored in the control module and can be retrieved using the Land Rover approved diagnostic system.
The suspension geometry changes when moving from off-road to access heights. See the following table for data:
Ride Height Tolerance Control
The air suspension control module has two ride height tolerance bands; normal tolerance and tight tolerance.
The control module considers the vehicle to be at target height if the current height is within the appropriate tolerance band. Height adjustments are not made until the vehicle height falls outside of the tolerance band for a pre-determined time. The time period is different depending on if the vehicle is moving or stationary. The tolerance bands are as follows:
^ Normal ± 10 mm
^ Tight ± 3 mm.
The tight tolerance band is only used if set by the Land Rover approved diagnostic system for diagnostic purposes or when the vehicle has been stationary for more than 5 minutes.
OPERATING MODES
The driver can manually select, using the air suspension switch, one of four ride states:
^ ON-ROAD - this height is the normal operating height of the vehicle
^ OFF-ROAD - this height is higher than the on-road height and provides improved ground clearance, approach, departure and breakover angles
^ ACCESS - this height is lower than the on-road height and makes entering and exiting the vehicle easier for the occupants
^ CRAWL (Locked at access) - this mode allows the vehicle to be driven at the access height at low speeds to provide increased roof clearance in low car parks etc.
HIGH SPEED - A non-selectable, automatic high speed mode is provided which lowers the vehicle height to improve vehicle handling.
NOTE:
Vehicle height changes are restricted if the air suspension control module receives a 'Door Open' signal from the GEM (generic electronic module) and the speed is less than 5 mph (8 km/h).
An additional 'TRANSPORTATION' mode is also available but is only selectable using the Land Rover approved diagnostic system. When this mode is active most vehicle systems, in addition to the air suspension, are inhibited or restricted to a minimal functionality.
If the air suspension control module senses that the vehicle has grounded and lost traction, the control module can temporarily increase and/or redistribute the volume of air supplied to the affected air spring(s) to maximize the available traction. This is known as extended mode and will be indicated to the driver by the lamps on the air suspension switch flashing.
If the air suspension control module senses that the vehicle is prevented from moving upwards or downwards during a height change or leveling correction, the control module will adopt a safe state and further height changes will be suspended.
If a fault is detected by the air suspension control module, the control module will reduce the system functionality dependent on the type and severity of the fault. The control module will also store a fault code which can be retrieved using the Land Rover approved diagnostic system. If a severe fault occurs, the control module will attempt to put the vehicle in a safe condition. A fault is relayed to the driver by the instrument cluster message center and an audible warning emitted from the instrument cluster.
If the detected fault is minor and does not affect vehicle safety, the instrument cluster message center will display the message 'SUSPENSION FAULT' and a chime will be emitted. The fault should be investigated and rectified as soon as possible.
If the detected fault is more serious, the message center will display the message 'SUSPENSION FAULT NORMAL HEIGHT ONLY' and a chime will be emitted. The fault should be investigated and rectified as soon as possible.
If the detected fault is more severe the message center will display the message 'SUSPENSION FAULT MAX SPEED 50KPH' and two chimes will be emitted every thirty seconds if this speed is exceeded. The message will change to 'SUSPENSION FAULT' when the vehicle speed is reduced to less than 31 mph (50 km/h). The vehicle should be driven slowly until the fault is rectified.
Air Suspension Control Switch
On-Road Mode
This is the normal ride height for the vehicle.
Off-Road Mode
Off-road mode will only be selectable if the vehicle speed is less than 25 mph (40 km/h). The vehicle will be raised 55 mm (2.2 in) higher than the on-road mode to provide additional body clearance and improved approach, departure and breakover angles. If the vehicle speed exceeds 31 mph (50 km/h), the air suspension control module will automatically lower the vehicle to the on-road mode height. At 25 to 28 mph (40 to 45 km/h) a message is displayed in the message center to warn the driver to slow down or the vehicle will lower.
Access Mode
Access mode lowers the vehicle body height by 40 mm (1.6 in) and provides easier entry, exit and loading of the vehicle. Access mode can be pre-selected when the vehicle is moving. The vehicle will partly lower as the vehicle speed decreases, lowering to the full access mode height when the vehicle reaches 5 mph (8 km/h). If the required road speed is not reached within a predetermined time, the air suspension will return the vehicle to the previously selected height.
Access mode can be selected at any vehicle speed. When access mode is selected, the response of the air suspension system will depend on the vehicle speed:
^ If the vehicle speed is more than 12.5 mph (20 km/h), the air suspension control module will wait for up to one minute for the vehicle speed to be reduced. The access mode LED (light emitting diode) and the lowering LED (light emitting diode) will flash while the air suspension control module waits for the vehicle speed to be reduced, the on-road mode lamp will remain illuminated. If the vehicle speed is not reduced sufficiently, the access mode request will be canceled after 1 minute.
^ If the vehicle speed is less than 12.5 mph (20 km/h), the air suspension control module will lower the suspension to a part lowered height and will remain at this height for up to one minute. The on-road mode lamp will extinguish as the air suspension control module lowers the suspension to the part lowered height. The access mode lamp and the lowering LED (light emitting diode) will illuminate. When part lowered is reached, the lowering LED (light emitting diode) will flash. If the vehicle speed is not reduced to less than 5 mph (8 km/h) in the one minute period, the access mode request will be canceled.
^ If the vehicle speed is less than 5 mph (8 km/h), the suspension will be lowered to access mode immediately. The access mode LED (light emitting diode) and the lowering LED (light emitting diode) will illuminate. When the access mode height is reached, the lowering LED (light emitting diode) will be extinguished.
Access height may be selected up to 40 seconds after the ignition is turned off, provided that the driver's door has not been opened within this time.
The suspension will automatically rise from access mode when the vehicle speed exceeds 6.2 mph (10 km/h). If access mode was selected directly from off-road mode then the system will return to off-road mode when the vehicle speed exceeds 6.2 mph (10 km/h). Otherwise the system will lift the suspension to On-road height.
Selecting Access Mode Directly from Off-Road Mode
When the suspension is in off-road mode height, pressing the 'Access' height change switch once, or pressing the lowering switch twice before the lowering LED (light emitting diode) is extinguished, the control module will lower the suspension to access mode height. The control module will remember to return the suspension to off-road height automatically if the vehicle speed increases above 6.2 mph (10 km/h).
Alternatively, pressing the drivers door module access switch once will perform the same function.
Crawl (Locked at Access) Mode
Crawl mode allows the vehicle to be driven at low speeds with the suspension locked at the access mode height. This allows the vehicle to be driven in low car parks etc. with increased roof clearance.
Crawl mode can be selected up to 21.7 mph (35 km/h) with a long press of the switch in a down direction. The access mode lamp and the crawl mode lamp will be illuminated. When the control module is in crawl mode, on-road mode height will be selected automatically if the vehicle speed exceeds 24.8 mph (40 km/h). At 18.6 to 21.7 mph (30 to 35 km/h) a message is displayed in the message center to warn the driver to slow down or the vehicle will raise. Crawl mode can also be manually canceled by moving the switch in the up direction for 1 second. The crawl mode lamp will now be extinguished.
High Speed Mode
High speed mode is a non-selectable, automatic mode which lowers the vehicle height by 20mm to improve vehicle handling. This feature is fully automated and is 'invisible' to the driver. If the vehicle speed exceeds 100 mph (160 km/h) for more than five seconds, the air suspension control module initiates the high speed mode. When the vehicle speed reduces to less than 80 mph (130 km/h) for more than 30 seconds, the vehicle returns to the On-Road height. This function is canceled if a trailer is connected to the trailer socket.
Automatic Height Change Warnings
When the suspension is in off-road mode, access mode or crawl mode height, the air suspension control module will change the suspension height automatically when the vehicle speed exceeds a predetermined threshold.
When the suspension is at off-road mode or crawl mode height, the control module issues a warning to advise the driver that the vehicle is approaching the speed threshold. The instrument cluster sounder will emit a chime, a message will be displayed in the message center and the on-road mode LED (light emitting diode) and either the raising or lowering LED (light emitting diode) will flash.
The off-road mode or crawl mode height speed warning is removed when the vehicle speed is reduced.
SPECIAL MODES
Door Open Functionality
If one or more of the vehicle doors are opened during a height change when the vehicle is stationary, the air suspension control module will restrict further height change. The door open signal is transmitted by the GEM (generic electronic module) on the K bus to the instrument cluster gateway and from the cluster is transmitted on the high speed CAN (controller area network) bus and received by the air suspension control module. This keeps the vehicle level to the set height when a door opens to allow for changes in loading conditions.
The LED (light emitting diode) on the air suspension LED (light emitting diode) display for the target mode height will remain illuminated and the raising or lowering LED (light emitting diode) will flash.
If all of the doors are closed within 90 seconds, the height change will resume. If the 90 second period is exceeded and all of the doors are not closed, the height change will be canceled. The mode LED (light emitting diode)'s showing the previously selected height and the target height will be illuminated. The mode height change can be reselected by operating the appropriate air suspension switch, however, if the vehicle is driven at speed of more than 5 mph (8 km/h) the control module will continue to raise or lower the vehicle to the target mode height.
Extended Mode
If the vehicle becomes grounded and the traction control becomes operational, the air suspension control module automatically increases the mass of air in the air springs to raise the vehicle clear of the obstruction. Extended mode is activated automatically and cannot be selected manually.
When the air suspension control module has activated the extended mode, the off-road mode lamp will flash if the suspension is above off-road mode height. The off-road mode and on-road mode lamps will flash if the suspension is between off-road mode and on-road mode heights. The on-road mode and access mode lamps will flash if the suspension is between on-road mode and access mode. A message will also be displayed in the message center.
To exit the extended mode, press the air suspension switch briefly in the up or down position or alternatively drive the vehicle at a speed of more than 2 mph (3 km/h) for 45 seconds.
Additional Lift in Extended Mode
When extended mode has been invoked and the automatic lifting of the vehicle is complete, the driver can request an additional lift of the vehicle. This can be particularly useful when extended mode has been activated on soft surfaces.
The additional lift can be requested once the height change LED (light emitting diode) has extinguished. Press and hold the air suspension switch in the up position for 3 seconds whilst simultaneously depressing the brake pedal. A chime from the instrument cluster will sound to confirm that the request has been accepted. The raising LED (light emitting diode) will be illuminated while the vehicle is being lifted.
Suspension Prevented From Moving
If the air suspension control module is attempting to change the suspension height and it detects that the suspension is prevented from moving, the control module will stop all suspension movement. This can be caused by jacking the vehicle, attempting to lower the vehicle onto an object or raising the vehicle against an obstruction.
The air suspension switch lamps operate as described for extended mode and the same message is displayed in the message center. To re-start the air suspension system operating, press the air suspension switch briefly in the up or down position or drive the vehicle at a speed of more than 2 mph (3 km/h) for 45 seconds.
Periodic Re-leveling
When the vehicle is parked, the air suspension control module 'wakes up' two hours after the ignition was last switched off and then once every six hours. The vehicle height is checked and if the vehicle is not level within a pre-set tolerance, small downwards height adjustments may be made automatically.
Transportation Mode
Transportation mode is a factory set mode which locks the suspension to enable the vehicle to be safely lashed to a transporter. The suspension transportation mode is automatically set when the vehicle is configured for transportation mode using the Land Rover approved diagnostic system. Transportation mode also affects other vehicle systems which are inhibited or restricted to a minimal functionality
When the ignition switch is switched off, the vehicle will be lowered onto the bump stops. This ensures that the securing straps do not become loose should air leak from the air springs.
When transportation mode is active, the air suspension switches are disabled. Periodic re-leveling is also disabled.
When the engine is started, the air suspension control module will cause the vehicle to rise to a height of -20mm to allow sufficient ground clearance for the vehicle to be loaded. While the height is changing, all the LED (light emitting diode)'s in the air suspension control switch will flash and a chime will be emitted by the instrument cluster. When the height of -20mm is reached, all the LED (light emitting diode)'s will illuminate continuously and the chime will stop.
When the engine is switched off, the air suspension control module will cause the vehicle to lower to a height of -60mm to allow the vehicle to be strapped down. While the height is changing, all the LED (light emitting diode)'s in the air suspension control switch will flash and a chime will be emitted by the instrument cluster. When the height of -60mm is reached, all the LED (light emitting diode)'s will illuminate continuously and the chime will stop.
Calibration Mode
This mode is used when the air suspension control module has been replaced or a height sensor or suspension component has been dismantled or replaced.
The following conditions apply when the vehicle is in calibration mode:
^ The ride height is set to tight tolerance
^ Fault reaction to VIN (vehicle identification number) mis-match with the Car Configuration File (CCF) is disabled
^ The raise, lower, access and hold switches are disabled
^ System is controlled to on-road height only.
AIR SUSPENSION COMPONENTS
The air suspension comprises the following:
^ Two front struts incorporating air springs
^ Two rear air springs
^ Front and rear valve blocks
^ Reservoir valve block incorporating a pressure sensor
^ An air reservoir
^ Four height sensors
^ Air supply unit
^ Air suspension control module
^ Air supply pipes
^ Air suspension control switch.
The air suspension system is controlled by the air suspension control module. The control module is mounted on a bracket adjacent the passenger side 'A' pillar.