Circuit/System Description
WARNING: This page is about a different car, the 2007 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT:
A new converter with less than 100 miles on it may set DTC P0420 due to out-gassing of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition.
A 3-way catalytic converter (TWC) controls emissions by converting hydrocarbons (HC) and carbon monoxide (CO) into carbon dioxide (CO2), and oxides of nitrogen (NOx) into nitrogen. The TWC also stores oxygen. When the listed driving conditions are met, the Catalyst System Efficiency test will run. The powertrain control module (PCM) monitors this oxygen storage capacity by comparing the pre and post-catalyst oxygen sensor signals while adding and subtracting fuel during specific driving conditions. The PCM compares the pre and post-catalyst oxygen sensor signals to determine if the oxygen storage capacity of the catalyst is degraded.