Conditions For Setting DTC
WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
The PCM detects that the HO2S 1 voltage switched from rich-to-lean fewer than 20 times within a 100 monitoring period or the PCM detects that the HO2S 1 voltage switched from lean-to-rich fewer than 20 times within a 100 monitoring period.