Heated Oxygen Sensor 2 (HO2S 2) Catalyst Monitor

CATALYST DESCRIPTION
To control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), a warm-up three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen.

CATALYST MONITORING
The PCM uses the H02S 2 to monitor the oxygen storage capability of the catalytic converter. Similar to the H02S 1, the H02S 2 reacts with the oxygen content in the exhaust stream after it passes through the catalytic converter. This voltage signal ranges from approximately 0.1 volt (high oxygen - lean mixture) to 0.9 volt (low oxygen - rich mixture). Unlike the HO2S 1, an H02S 2 signal that appears lazy or inactive is normal. The PCM compares readings from both the front HO2S 1 and the H02S 2 in order to determine the efficiency of the catalyst.