Conditions for Setting the DTC
WARNING: This page is about a different car, the 2006 GMC Yukon XL, 2006 Chevrolet Suburban, and 2006 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The PCM detects that the affected HO2S rich-to-lean or lean-to-rich average response time is more than a calibrated value for 100 seconds.