The readings provided by the Oxygen Sensors (O2) are used by the Power Train Control Module (PCM) to determine the oxygen content in the exhaust system. Each of these sensors has a heating element whose objective is to reduce the time it takes to have a closed cycle.
The PCM is the one that controls the ignition time of said heater, in addition it constantly monitors the circuits of the heater in search of voltages or in some cases amperages that are outside the expected level.
If the Powertrain Control Module (PCM) detects a high voltage condition in excess, the DTC code P0038 OBDII is set in the circuit of the heating element.