2002 Nissan Altima I replaced catylist &crank pos senser and

Question

Still get codes P1456 and PO420 after replacing catalyst and crankshaft positioning sensor

Answer 1

For p01456 there is probably an evap leak, try to take it to a mechanic that has a evap smoke  

you can try to replace your gas cap as a first step. 

 

- Missing Fuel cap

- Incorrect fuel filler cap used

- Fuel filler cap remains open or fails to close

- Foreign matter caught in fuel filler cap

- Incorrect fuel tank vacuum relief valve

- Leak is in line between intake manifold and EVAP canister purge volume control solenoid valve.

https://www.autocodes.com/p1456_nissan.html