Conditions for Setting the DTCs
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 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 603 mV for greater than 20 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 603 mV, this DTC sets.