Question

what does P1456 means for 2003 nissan altima.

Answer 1

Hi there,

This is sort of a default code and a catch all. Basically the car knows there is a problem wiht the evap system, but doesn't know where. Sadly this can just about be any part of the system. With this code I would start with a smoke test to check for leaks, if none are found then the sensors and the purge and canister valves need to be tested.