Conditions for Setting the DTC
WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The ECM detects the internal HO2S signal voltage is less than 0.2 volts or more than 4.7 volts for more than 1 second.