July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!
Rail Pressure Sensor (RPS): Specification
WARNING: This page is about a different car, the 2015 Kia Forte5 and 2015 Kia Forte Koup. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Rail Pressure Sensor Output Voltage Versus Pressure Graph