If a system has a leak, the compressor will have to work harder to keep the vehicle at the same ride height, and gets hotter the longer it has to work. Excess heat can cause premature wear of the piston rings, and, if the leak goes unchecked, it can cause the compressor to fail completely. When the pump fails, oil and metal debris can enter into the valves, reservoirs and bladders.
The computer module controlling the pump keeps track of how long the compressor has run and how long the correction should take. If a correction to ride height takes too long, the system knows that the compressor could overheat, so it can set a code and then disable the pump before it's damaged.
Almost every air ride vehicle has a self-diagnostic process that occurs during startup. On some vehicles, if the self-check detects a problem, it will disable the system or put it in a fail-safe mode and alert the driver. It will also set a soft or pending "C" (chassis) code.
