P013A or P013C
WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
The ECM determines that the response time for the HO2S 2 signal voltage to switch from greater than 400 mV to less than 200 mV is greater than 500 mS. The condition exists for greater than 4 seconds or for a cumulative time of 30 seconds.