is fixing the problem as simple as getting a new gas cap?

Question

Engine light is on had it scanned code p0455 comes up

Answer 1

P0455 EVAP system large leak

Most of the time when it is a large leak the fuel cap not being secured or being refueled and the engine is running , this is the easy and in a majority time is the cause. In other time a scan tool is need to read the fuel tank pressure sensor