Function Explanation (DTC Detection Outline)

The PCM closes the purge solenoid valve and CV solenoid valve while the vehicle is being driven, and seals the fuel tank. By opening the purge solenoid valve after sealing the fuel tank, evaporative gas in the fuel tank is inducted into the intake manifold, fuel tank pressure is reduced, and the pressure change of the fuel tank is measured by the fuel tank pressure sensor. If the pressure of the fuel tank does not reach the target vacuum after the specified time has elapsed since the pressure was measured, the PCM determines that there is an evaporative gas leakage. If the PCM determines that refueling was performed before the engine starts, according to the result of the refueling determination, the PCM determines that the fuel-filler cap is open and stores DTC P0457:00 (if PCM determines that refueling is not performed, it stores DTC P0455:00).
If the fuel tank level increases after the engine starts, the PCM determines that refueling is performed by comparing the fuel tank level before one drive cycle with the fuel tank level after engine start.

Fig 1: Purge Solenoid Valve Drive Signal Waveform
Courtesy of MAZDA MOTORS CORP.