If the air suspension control module loses communications with the ABS module or the ABS module reports
a fault, the air suspension control module immediately returns to the 'default' height, which is below the on-
road ride height. Once at the default height, the control module will continue to level the vehicle at this
height. It is unlikely that the fault will be in the air suspension control module. When the fault is repaired, the
air suspension control module will resume full functionality but the error will remain in the control module
memory.
For major faults the control module will not level the vehicle at the 'current' ride height. The control module freezes height
changes until it receives a manual or automatic request for height change. The control module will return to standard height
if possible and freezes once standard height is achieved.
If the suspension is above the on-road height and the air suspension control module cannot lower the suspension, all height
changes will be frozen. The control module will issue a message on the high speed CAN bus which is received by the
instrument cluster which displays a maximum advisable speed in the message center. An immediate 'freeze' of the vehicle
height is caused by the following:
Failure of more than one height sensor - vehicle on bump stops
Implausible articulation symptoms detected - vehicle on bump stops
Valve or solenoid failure - corner valve stuck open below on-road mode height or exhaust valve stuck shut above
on-road mode height
Stuck corner or whole vehicle (diagnosed using plausibility of the sensor inputs).
If height change is not possible, e.g. exhaust valve failed closed at off-road height or compressor failed at access height, the
control module will not level or change height.
If the air suspension control module has a hardware fault, the control module will disable all air suspension functions.
Detectable hardware errors include memory error, control module failure and calibration errors.
Fault Messages
The air suspension has two methods which it can use to inform the driver of a fault in the air suspension system; the air
suspension switch LED's and the instrument cluster message center.
When minor faults occur and the air suspension control module is able to level the vehicle to the 'current' ride height, the air
suspension switch LED's will display the current ride height.
If the air suspension control module suffers a major failure and there is no air suspension control, all the control switch
LED's will remain off.
If a fault occurs and the air suspension control module can determine the ride height and the vehicle is not above on-road
mode height, the driver will be notified via a 'air suspension fault max speed 18.6 mph (30 km/h)' message in the message
center.
If the control module cannot determine the height of the vehicle, or the vehicle is above on-road mode height, cannot be
lowered and the vehicle speed is too high, an air suspension fault message is displayed.
If the vehicle is restricted to on-road mode height an air suspension fault normal height only message is displayed.
AIR SUSPENSION SWITCH