Why would my po456 code only come on when fuel gauge shows 1/4 tank??

Question

Fuel tank
1/4 tank gas
Light

Answer 1

P0456 Evaporative emission system leak detected (small leak detected)

The EVAP monitor system only runs when the fuel tank is between 1/4 to 3/4. What the EVAP system uses is a canister vent solenoid which is sealed during a EVAP system check, From here the canister purge valve is used to obtain a target vacuum during a EVAP leak check. Just because the fuel gauge reads 1/4 the code P0456 was pending, until the monitor turned off. For small EVAP leaks your best move is replace the fuel cap.