Part 2
Vehicle Dynamic Suspension
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 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, the message 'CONFIRM REQUIRED SUSPENSION HEIGHT' will be displayed in the instrument cluster.
Extended Modes
Raise Inhibit Raise inhibit is a reactive mode invoked when the following conditions are satisfied, vehicle speed below 10kph and vehicle raising very slowly. Raise inhibit is normally invoked when vehicle is lifting against an obstacle, it can also be used when the vehicle is winching or is tethered down.
Jacking Jacking is a reactive mode invoked when the following conditions are satisfied, vehicle stationary, system attempts to level the vehicle down and rate of vehicle lowering is below a predefined threshold for a predefined time. Jacking mode is normally invoked under the following conditions, vehicle jacking or vehicle grounded and stationary
Lower Inhibit Lower inhibit is a reactive mode invoked when the following conditions are satisfied, vehicle stationary, rate of vehicle lowering is below a predefined threshold for a predefined time. Lower inhibit is normally invoked under the following conditions, vehicle lowered onto an obstacle during a height change.
Belly-Out Belly-Out is a pro-active mode invoked when the following conditions are satisfied, vehicle moving and speed is below 50kph, traction activity is induced on axle pairs for fixed period of time and wheel heights above a predetermined threshold on coinciding axle pairs for the same fixed period of time. Belly-Out is normally invoked under the following condition, vehicle is attempting to move and with low levels of traction and supported by an obstacle.
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.
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 twenty four 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 delivery mode using the Land Rover approved diagnostic system. Delivery 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 to access mode. 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-levelling is also disabled.
When the engine is started, the air suspension control module will cause the vehicle to rise allowing 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 sufficient height 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 allowing 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. When the height of -50mm is reached, all the LED (light emitting diode)'s will illuminate continuously.
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
- Message "Air suspension not in customer mode" is displayed in the instrument pack.
Remote Operation
The buttons on the Smart Key may be used to operate the air suspension system, allowing the vehicle to be raised or lowered remotely. This may be useful in attaching a trailer or loading the vehicle.
To change the suspension height using the Smart Key, the vehicle must be stationary, all the doors closed and the hazard warning lamps switched on.
To raise the vehicle suspension buttons 1 and 2 to are to be press simultaneously.
To lower the vehicle suspension buttons 1 and 3 to are to be press simultaneously
Air Harness
The air harness comprises ten separate nylon pipes which are connected between the system components with Voss connectors. The pipes have the following diameters:
If a pipe becomes damaged, an in-line connector is available for repair purposes. The pipes are secured to the body and chassis with a number of plastic clips.
LEAK DETECTION
Leak detection can be carried out using a Land Rover approved leak detection spray.
If the vehicle appears to be leaking, perform a leak check on all aspects of the system, i.e.; air spring hose fittings and the associated connections on the valve blocks, air springs and reservoir. Failure to correctly diagnose leakage will result in unnecessary exchange of serviceable components and recurrence of original problem.
AIR SUSPENSION COMPONENTS
Valve Blocks
Front and Rear Valve Blocks
Reservoir Valve Block
Front and Rear Valve Blocks
The front and rear axle valve blocks are similar in their design and construction and control the air supply and distribution to the front or rear pairs of air spring damper modules respectively. The difference between the two valves is the connections from the valve block to the left and right hand air spring damper modules and the valve size. It is important that the correct valve block is fitted to the correct axle. Fitting the incorrect valve block will not stop the air suspension system from functioning but will result in slow raise and lower times and uneven raising and lowering between the front and rear axles.
The front valve block is attached to the RH (right-hand) end of the front bumper armature assembly. The valve block has three attachment lugs which are fitted with isolation rubber mounts. The rubber mounts locate in slots in the armature. The valve lugs locate in the holes above the slots and are pushed downwards into positive location in the slots.
The rear valve block is located on the forward face of the left hand rear suspension turret. The valve block has three attachment lugs which are fitted with isolation rubber mounts which locate in a bracket with three slotted holes. The bracket is attached to the left hand side of the chassis. The isolation rubber mounts locate in the 'V' shaped slots and are pushed downwards into positive location in the slots.
The front and rear valve blocks each have three air pipe connections which use 'Voss' type air fittings. One connection is an air pressure inlet/outlet from the reservoir valve block. The remaining two connections provide the pressure connections to the left and right hand air springs.
Each valve block contains three solenoid operated valves; two corner valves and one cross-link valve. Each of the valve solenoids is individually controlled by the air suspension control module. The solenoids have a resistance value of 2 Ohms at a temperature of 20°C (68°F).
Reservoir Valve Block
The reservoir valve block is attached to a bracket on the outside of the left hand chassis rail, between the reservoir and the air supply unit. The valve block is located within the air supply unit acoustic box to protect it from dirt ingress and damage from stones. The valve block has three attachment lugs which are fitted with isolation rubber mounts. The rubber mounts locate in the chassis bracket which has three corresponding 'V' shaped slots. The rubber mounts are pushed downwards into positive location in the slots.
The reservoir valve block controls the storage and distribution of air from the reservoir. The reservoir valve block also contains the system's pressure sensor.
The valve block has four air pipe connections which use 'Voss' type air fittings. The connections provide for air supply from the air supply unit, air supply to and from the reservoir and air supply to and from the front and rear valve blocks. The connections from the air supply unit and the front and rear control valves are all connected via a common gallery within the valve and therefore are all subject to the same air pressures.
The valve block contains a solenoid operated valve which is controlled by the air suspension control module. The solenoid valve controls the pressure supply to and from the reservoir. The solenoid has a resistance value of 2 Ohms at a temperature of 20°C (68°F). When energized, the valve spool moves allowing air to pass to or from the reservoir.
The valve block also contains a pressure sensor which can be used to measure the system air pressure in the air springs and the reservoir. The pressure sensor is connected via a harness connector to the air suspension control module. The control module provides a 5V reference voltage to the pressure sensor and monitors the return signal voltage from the sensor.
Using this sensor, the control module controls the air supply unit operation and therefore limits the nominal system operating pressure to 244 lbf/in2 (16.8 bar gage).
Removal of the reservoir valve block will require full depressurization of the reservoir. The valve block is a non-serviceable item and should not be disassembled other than for replacement of the pressure sensor.
Air Supply Unit
The air supply unit is located on the outside of the left hand chassis rail, forward of the upper control arm. The unit is attached to the chassis rail with three bolts and is protected by an acoustic box.
Acoustic Box
The acoustic box, which comprises of two parts; upper and lower, surrounds the air supply unit. The acoustic box is a plastic moulding which is lined with an insulating foam which controls the operating noise of the air supply unit. The reservoir valve block is also located in the acoustic box, forward of the air supply unit.
The air supply unit comprises the following major components:
- A piston compressor
- A 12V electric motor
- A solenoid operated pilot valve
- An exhaust valve
- An air dryer unit
The air supply unit supplies dry, compressed air into the air suspension system where it is directed into the air springs or the reservoir by solenoid operated valves. Air can be exhausted from the system when required by the opening of an air spring or reservoir valve in addition to the exhaust valve which is part of the air supply unit.
The compressor operates to pressurize either the reservoir or to inflate one or more of the air springs. Height changes of less than 20 mm are achieved using the compressor alone. Height changes of more than 20 mm are achieved using the reservoir and the compressor. The compressor cannot operate without the engine running, with the following exceptions:
- During remote operation to raise the vehicle to allow for the attachment of a trailer
- When under control of a Land Rover approved diagnostic system.
The air supply unit can be serviced in the event of component failure, but is limited to the following components; air dryer, pilot exhaust pipe and the rubber mounts.
The air supply unit is attached to a bracket which is bolted to the chassis. The unit is mounted to the bracket with flexible isolation mounting rubbers which assist with preventing operating noise being transmitted to the chassis.
Removal of the air supply unit does not require the whole air suspension system to be depressurized. The front and rear valve blocks and the reservoir valve block are normally closed when de-energized, preventing air pressure in the air springs and the reservoir escaping when the unit is disconnected.
There are a number of conditions that will inhibit operation of the air supply unit. It is vitally important that these system inhibits are not confused with a system malfunction. A full list of air supply unit inhibits are given in the compressor section of this document.