Circuit Description

The DTC P0140 Heated Oxygen Sensor (HO2S) Circuit Sensor 2 diagnostic monitors the output of the post catalyst HO2S. The Powertrain Control Module (PCM) has the ability to determine the efficiency of the three-way catalytic (TWC) converter using the HO2S 1 and the HO2S 2. The HO2S produces a voltage between 100-900 mV that varies depending upon the oxygen content of the exhaust stream. The HO2S 1 output signal indicates the amount of oxygen present in the exhaust gases entering the TWC converter. The HO2S 2 output signal indicates the oxygen storage capacity of the catalyst in the TWC converter. The oxygen storage capacity of the catalyst is an indicator of the effectiveness of the TWC converter. The HO2S 1 output signal is more active than the HO2S 2 output signal when the catalyst is operating efficiently.