Theory Of Operation
WARNING: This page is about a different car, the 2016 RAM 3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
The purpose of the diagnostic is to check the PTO switch circuit for open or short to ground conditions. This PTO ground switch (Field Effect Transistor) is a low side driver used to control the PTO solenoid. If the feedback circuit voltage is high while the TCM is commanding the PTO ground switch OFF (low), a DTC will be set.