Catalyst monitoring: Description: General description
The solution chosen to fulfill this OBD requirement is based on Oxygen Storage Capacity (OSC):
During the diagnosis (special A/F pulses during engine steady state conditions), the downstream O2 sensor signal is analyzed to evaluate the OSC of the catalyst.
The OSC is correlated experimentally with the global hydrocarbon (HC) efficiency and HC emissions during the test cycle. It represents the quantity of oxygen that is really used for the oxidation-reduction reaction by the catalytic converter (stored during the lean excursion and consumed during the rich excursion).