Conditions for Setting the DTC

WARNING: This page is about a different car, the 2004 Buick Rendezvous. 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.
OR
If the ECM detects that the rear HO2S voltage is less than 499 mV and the Desired HO2S 1 Lambda is less than 0.850 for more than 5 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 2 voltage is still less than 499 mV, this DTC sets.