DTC P0154: Ho2S Circuit - Insufficient Activity - Bank 2, Sensor 1: Description
WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
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 (O2S) varies the voltage within a range of about 1000 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 HO2S high signal or sensor HO2S low signal circuit.