O2 Sensor Contamination
WARNING: This page is about a different car, the 1994 Chevrolet Caprice and 1994 Buick Roadmaster. 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.