O2 Sensor Contamination
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1993 Pontiac Sunbird, 1993 Pontiac Grand Prix, 1993 Oldsmobile Cutlass Supreme, 1993 Chevrolet Lumina, and 1993 Chevrolet Corsica. However, it is still accessible from the selected car via links, so may be relevant.
O2 sensor contamination, caused by silicone in certain fuels or use of improper RTV sealant, may cause a White powdery coating to cover exterior of O2 sensor. False high signal voltage (low oxygen content sensed) produced is interpreted by control module as a rich mixture, causing control module to set Code 45.