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.
Ensure no corrosion is present in the HO2S bank 1 sensor 1 harness connector. Make sure no exhaust leaks exist between the bank 1 engine head and HO2S bank 1 sensor 2. Each of these two conditions may set P0133. The most probable cause for DTC P0133 is a weak, aging or contaminated sensor. Check for obvious contamination (oil, fuel or engine coolant) by removing sensor. Source and fix the cause of the contamination if contaminated. Replace the HO2S bank 1 sensor 1.