WARNING: This page is about a different car, the 2018 Kia Forte5 and 2018 Kia Forte. However, it is still accessible from the selected car via links, so may be relevant.
Connect the KDS on the Data Link Connector (DLC).
Measure the output voltage of the RPS at idle and various engine speed.
Fig 1: Rail Pressure Sensor (RPS) Output Voltage Graph