Possible Causes

WARNING: This page is about a different car, the 2002 Nissan Pathfinder and 2002 Infiniti QX4. However, it is still accessible from the selected car via links, so may be relevant.

ECM illuminates MIL and sets DTC P1448, when EVAP-CVCV remains open under certain driving conditions. Possible causes are:

Defective EVAP-CVCV.
Faulty EVAP Control System Pressure Sensor (EVAP-CSPS) or circuit.
Blockage in EVAP-CVCV hose.
Defective water separator.
EVAP canister saturated with water.
Defective EVAP vacuum cut valve.