Conditions for Setting the DTCs
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 length of time for the HO2S 1 to switch from lean to rich and back to lean, which is called a switching cycle, has exceeded a predetermined threshold. The condition exists for 2 cycles out of a 12 cycle test sample.