L322 Range Rover System Description and Operation
SUSPENSION
DESCRIPTION AND OPERATION
60-17
Normal Mode
The air suspension ECU will enter normal mode when it receives a 'wake up' signal from the Body Control Unit (BCU).
The BCU will provide the 'wake up' signal when the following occurs:
l
A door is opened.
l
The vehicle is unlocked using the remote handset.
l
The ignition is switched on.
The BCU will continue to supply the 'wake up' signal for 15 minutes after the ignition is switched off. The air
suspension ECU will then remain active for a further 10–15 seconds to enable any new data to be written to its
Electronic Erasable Programmable Read Only Memory (EEPROM).
If the BCU has supplied a 'wake up' signal, but the ignition is off, the air suspension ECU will enter an Inactive Mode.
Under these circumstances, air suspension functionality is reduced. Although the air suspension ECU will continue to
monitor vehicle ride height and make any necessary adjustments, to keep the vehicle at the correct height, all ride
height selections made via the rotary switch will be ignored. The ECU will not illuminate the LED's or allow the
compressor to fill the reservoir. If a height increase is necessary and the pressure in the air reservoir is below 9 bar
(130 lbf/in
2
), the ECU will power the compressor to raise the vehicle back to the correct height.
If the ignition is switched on but the engine is not running, the air suspension ECU will continue to monitor vehicle ride
height and make any necessary adjustments. Downwards ride height selections made via the rotary switch will be
accepted, and the LED's will illuminate as normal. Upward ride height selections made via the rotary control switch
will be rejected. However, if the vehicle height decreases (e.g. if a load is added to the car), the ECU will return the
vehicle to the current ride height. These height changes are made using the air suspension reservoir providing the
available air pressure is more than 9 bar (130 lbf/in
2
). If the air pressure is less than 9 bar (130 lbf/in
2
), the compressor
is used for the height changes. Filling of the reservoir remains inhibited.
Periodic Wake-Up Mode
When the 'wake up' signal is removed by the BCU, the air suspension ECU powers down. After it powers down, the
air suspension ECU will wake up approximately every six hours and level the vehicle ride height. The air suspension
ECU will determine which corner of the vehicle is lowest, and adjust the remaining corners to the same level. This
action takes approximately 6–10 seconds to perform. The air suspension ECU will then remain active for a further 10–
15 seconds to enable any new data to be written to its EEPROM.
If the air suspension ECU fails to level the vehicle (if there is an obstruction beneath the vehicle for instance), periodic
wake-up mode will be suspended until the air suspension ECU receives a wake-up signal from the BCU.
NOTE: The air suspension ECU will not raise the vehicle in this mode.
Transportation Mode
To enable the vehicle to be delivered safely from the factory to the dealership, the air suspension system is set in
transportation mode. When the engine is running, the ride height will be set at 'Transportation High', which is 20 mm
below standard ride height. All four LED's will remain illuminated.
When the engine is not running, the air suspension ECU will drop the ride height by 50 mm (Transportation Low). All
four LED's will flash.
When the ride height is at 'Transportation Low' the vehicle can be lashed to a transporter, without the risk of loosening
due to the suspension ride height lowering.