Federal Models

With engine at normal operating temperature, disconnect hoses to check valve and relief valve from air hose connector and cap off connector. See Fig 1.
Increase engine speed to 3000 RPM and place hand over air outlet of relief valve to check for discharged air. If no air is felt, replace relief valve.

Fig 1: Checking Air Pump Relief Valve
Courtesy of NISSAN NORTH AMERICA, INC.