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 2 voltage is greater than 650 mV for greater than 20 seconds, then an intrusive test is performed. The ECM will lean the fuel mixture up to -7 percent and then wait for 10 seconds at -7 percent. If the ECM detects that the HO2S 2 voltage is still greater than 650 mV, the ECM then tests the HO2S 2 at the next decel fuel cut-off. If the ECM detects the HO2S 2 voltage is greater than 140 mV after 4 seconds in decel fuel cut-off, this DTC sets.