Theory of Operation
WARNING: This page is about a different car, the 2011 RAM Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The Oxygen Sensor is an input to the Smart Oxygen Sensor Module. This module is a smart device that receives information, such as dew point flag, engine speed, etc., via the J1939 BUS from the primary Powertrain Control Module (PCM). It provides PCM with the oxygen concentration signal. It also performs its own diagnostics and reports failures back to the primary engine PCM using the J1939 BUS. The PCM then decodes the error message and converts it to a fault code.