Diagnostic Aids
WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
If an HO2S bank 2 sensor 1 heater control circuit DTC is also set, diagnose that DTC first. A heater control circuit DTC that is active for a certain length of time will set this DTC. Then, if P0154 is also set, diagnose that DTC next. See DTC P0154: HO2S CIRCUIT - INSUFFICIENT ACTIVITY - BANK 2, SENSOR 1 . An open in the sensor signal or sensor return may set DTC P0155.
Heater element resistance should be 7.0-20.2 ohms.