O2 Sensor Contamination
WARNING: This page does not describe the selected car, but rather 19 other vehicles, including the 1996 Chevrolet Chevy Van, 1995 GMC Yukon, 1995 GMC Vandura Special, 1995 GMC Vandura, and 1995 GMC Suburban. 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 O2 sensor. The false high signal voltage produced (or low oxygen content sensed) is interpreted by control module as a rich mixture, causing control module to set Code 45.