Conditions For Setting DTC

WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

The vehicle is in Closed Loop fuel control, based on the HO2S voltages switching from below 350 mV to above 500 mV.
The PCM monitors the HO2S voltages for 120 seconds.
During the 120 second monitoring period, the voltage remains within 350-500 mV for approximately 16 seconds.