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.
If the ECM detects that the rear HO2S voltage is less than 740 mV for more than 100 seconds, then an intrusive test is performed. The ECM will enrich the fuel mixture up to 30 percent and then wait for 10 seconds at 30 percent. If the ECM detects that the HO2S voltage is still less than 740 mV, this DTC sets.