DTC P0140: Ho2S Circuit Insufficient Activity - Sensor 2 (Regal): Description
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The Powertrain Control Module (PCM) supplies a bias voltage of about 450 millivolts between the Heated Oxygen Sensor (HO2S) high signal circuits and the low signal circuits. When measured with a 10-megaohm DMM, this may display as low as 320 millivolts. The HO2S varies the voltage within a range of about 1000 millivolts when the exhaust is rich, down through about 10 millivolts when exhaust is lean. The PCM constantly monitors the HO2S signal during closed loop operation, and compensates for a rich or a lean condition by decreasing or increasing the injector pulse width as necessary. If the HO2S 2 voltage remains at or near the 450 millivolts bias for an extended time, DTC P0140 will set.