DTC C1808: Integral Time Malfunction Supplying Air: Description
WARNING: This page is about a different car, the 2013 Nissan Armada. However, it is still accessible from the selected car via links, so may be relevant.
The suspension air compressor is supplied power by the compressor motor relay. The suspension control unit supplies power to the compressor motor relay in order to activate the relay and subsequently activate the suspension air compressor.