I have attached what the code is. And it does indicate a very large leak like the gas cap being off or loose. My suggestion is ensure the gas cap is secure, clear the codes and see if it returns. There are some checks for the system if you have the proper tester. It is the CONSULT-II for a Nissan. I can attach that if you want and have the tester.
Hope this helps
NOTE: If DTC P0455 is displayed with P1448, perform trouble diagnosis for DTC P1448 first. See: P1148
This diagnosis detects a very large leak (fuel filler cap fell off etc.) In EVAP system between the fuel tank and EVAP canister purge volume control solenoid valve.
" Use only a genuine NISSAN fuel filler cap as a replacement. If an incorrect fuel filler cap is used, the MIL may come on.
" If the fuel filler cap is not tightened properly, the MIL may come on.
" Use only a genuine NISSAN rubber tube as a replacement.
Thursday, October 30th, 2008 AT 11:29 AM