The purpose of the calibration called "All Pump Pressure" is to teach the Machine Controller (called Machine ECM) how to best control the Main Pumps flow.

Indeed, at the end of this calibration, the Machine ECM will exactly know and record the relationship between the current it sends to the Pump Control Solenoid and the resulting actual Pump Displacement.

This calibration will be run for each of the 2 main pumps.