Both the fuel, charging and cambio pin are displayed in the app and can be called up permanently during the active rental, if required.
You set up the hvv switch pin yourself when you registered and should therefore know it. It is required, among other things, to confirm bookings and cancelations.
The fuel pin is required to legitimize the payment process by credit card at the petrol station.
The charging pin is required to open the corresponding charging station with the charging card.
And last but not least: Entering the Cambio pin into the on-board computer of a Cambio car is required to release the ignition key.