HO2S 2 (Catalyst Monitor)

In order to control emissions of Hydrocarbons (HC), Carbon Monoxide (CO) and Oxides Of Nitrogen (NOx), away catalytic convener is used. The catalyst within the convener promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas, convening them into harmless water vapor and carbon dioxide. The catalyst also converts the NOx to nitrogen. The VCM has the capability to monitor this process using HO2S 2. The HO2S 2, located in the exhaust stream past the 3-way catalytic convener, produces an output signal which indicates the oxygen storage capacity of the catalyst. This in turn indicates the catalyst's ability to covert exhaust emissions effectively. A problem with the HO2S 2 electrical circuits should set DTC P0137, P0138 or P0140, depending on the specific condition. If the catalyst is functioning correctly, the HO2S 2 signal will be far less active than that produced by the HO2S 1. If a problem exists which causes the VCM to detect excessive HO2S 2 activity outside of an acceptable range for an extended period of time, the VCM will set DTC P0420, indicating that the 3-way catalytic converters oxygen storage capacity is below a threshold considered acceptable.