Possible Causes

WARNING: This page is about a different car, the 2003 Nissan Pathfinder. 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.