New regulations for exhaust gas emissions for motor vehicles continue to provide challenges for emission and onboard diagnostic (OBD) compliance. Such regulations require that levels of hydrocarbons (HC), carbon monoxide (CO), and nitrogen monoxide (NO) in exhaust gas exiting an exhaust system of a motor vehicle be below predefined levels set by one or more government agencies and regulations, e.g. the Clean Air Act.
The use of automotive emissions catalysts to help control levels of HC, CO, and NO is known. One type of catalyst, known as an oxidation catalyst, typically contains a metal such as platinum, palladium, or rhodium which assists in oxidizing HC to CO2 and water (H2O), CO to CO2, and NO to NO2.
Oxidation catalysts are known to decrease in efficiency with prolonged use and thus monitoring and detecting of degradation of the catalysts is desired in order to ensure levels of HC, CO and NO are maintained below the predefine levels. However, conventional monitoring and detection techniques require additional sensors, equipment, etc., to determine if an oxidation catalyst is performing properly or decreasing in efficiency. Accordingly, a need exists for alternative OBD monitoring systems and methods that can determine if an oxidation catalyst in a vehicle exhaust gas system is performing properly without the use of additional sensors, equipment, etc. that are part of a conventional vehicle exhaust and OBD system.