DTC P0140: Ho2S Circuit - Insufficient Activity - Bank 1, Sensor 2: 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.

In order to control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a 3-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and the CO present in the exhaust gas, converting these chemicals into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting the NOx to nitrogen. The Powertrain Control Module (PCM) has the ability to monitor this process using the post-catalyst Heated Oxygen Sensor (HO2S). This sensor produces an output signal which indicates the oxygen storage capacity of the catalyst; this in turn indicates the catalyst's ability to convert exhaust gases efficiently. If the post HO2S signal voltage remains at or near the 450 mV bias for an extended period of time, this Diagnostic Trouble Code (DTC) will set.