Large EVAP Leak Detection
WARNING: This page is about a different car, the 2021 Kia Seltos. However, it is still accessible from the selected car via links, so may be relevant.
The PCSV is opened with a certain increase for the pressure to reach down to a certain level. If the pressure can't be lowered below a threshold, the system is regarded as having a fuel cap-open or having a large leak.