DTC P0134: Ho2S Circuit - Insufficient Activity - Bank 1, Sensor 1: Description

The Powertrain Control Module (PCM) supplies a bias voltage of about 450 mV between the Heated Oxygen Sensor (HO2S) high signal and low signal circuits. When measured with a DMM, this may display as low as 320 mV. The oxygen sensor varies the voltage within a range of about 1,000 mV when the exhaust is rich, down through about 10 mV when exhaust is lean. The PCM constantly monitors the HO2S signal during Closed Loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If the HO2S voltage remains at or near the 450 mV bias for an extended period of time, this Diagnostic Trouble Code (DTC) will be set, indicating an open sensor signal or sensor low circuit.