Theory Of Operation
WARNING: This page is about a different car, the 2013 RAM 1500. However, it is still accessible from the selected car via links, so may be relevant.
The purpose of the diagnostic is to monitor the rationality of the park pawl sensor signal. The sensor has two pins to determine the position of the park pawl and two types of faults are monitored: If the voltage output of the sensor is low or the sensor is too long in the intermediate position, DTC P0851 will set.