DTC P0456: EVAP Control System - Very Small Leak: Description
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.
This diagnosis detects very small leaks in the EVAP purge line between the fuel tank and EVAP Canister Purge Volume Control Solenoid Valve (EVAP-CPVCSV) using engine intake manifold vacuum. If ECM determines leak to be a very small leak, DTC P0456 will set. If ECM determines leak to be a small leak, DTC P0442 will set.