EAS Height Sensors:
Under normal operating conditions, the air suspension ECU keeps the vehicle level at the 'current' ride height. The
incoming height signals from the sensors are passed through filters to remove irregular signals produced by road
noise or other irregularities. When the vehicle is stationary or a height change is in progress, the signals are passed
through a 'fast' filter. The 'fast' filtered signals track the true rate of change of height when the vehicle height is
changed and can also remove road noise when the vehicle is driving. When the vehicle is moving, the signals are
passed through a 'slow' filter. The 'slow' filtered signals remove almost all road noise from the signals and output a
true long term average for each corner height. The 'slow' filtered signals cannot be used to respond quickly during
height changes.
The air suspension ECU monitors each corner height signal using the fast filtered signals if the vehicle is stationary
or the slow filtered signals if the vehicle is moving. If the height remains in a 'dead band' which is ±10 mm from the
target height, the ECU does not implement any height adjustment changes. When the ECU detects that a corner has
moved outside of the 'dead band', the ECU operates the compressor and/or the valves to raise or lower the
corresponding corner(s) back into the target height.
When the engine is not running, the 'dead band' target height tolerance is increased to +20 mm and -25 mm. During
'wake-up', the tolerance band is ±20 mm. In all cases, the ECU will bring the corner height as close as possible to the
target height. The ECU monitors the rate of change of height of the corner signals to predict when to close the valve
so that the target height is not overshot.