This 1's easy:
The pcm will flash you an error on your dash panel & disable the air system before it just breaks.
If you overload your truck in Normal mode for example, the pcm has preset parameters for the height of each mode by way of low voltage sent from the ride height sensors attached to each air spring. The weight of the load will send the sensor levers into a lower or higher position, depending on front or rear, changing the voltage to a value outside of the preset acceptable parameters, setting off a failsafe mode within the pcm. The compressor will then cease to pump air into the air springs until a correction in the load has been made to place the sensors back into the preset acceptable parameters.