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

Powertrain Control Module (PCM) supplies a bias voltage of about 450 mV between Heated Oxygen Sensor (HO2S) high signal and low signal circuits. When measured with a DVOM, this may display as low as 320 mV. Oxygen sensor varies voltage within a range of about 1000 mV when exhaust is rich, down to about 10 mV when exhaust is lean. PCM constantly monitors HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If HO2S voltage remains at or near 450 mV bias for an extended period of time, this DTC will set, indicating an open sensor signal or sensor low circuit.