Theory Of Operation
WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
The purpose of the diagnostic is to detect electrical failures in the power supply of the solenoid and pressure regulator output stages. Diagnostics are performed in the microcontroller as well as the output stage ASICs. The open circuit diagnostics are performed in the output stage ASICs and the other electrical diagnostics are performed in the microcontroller.