O2 Sensor Contamination
WARNING: This page is about a different car, the 1995 GMC Sonoma and 1995 Chevrolet S10 Pickup. 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.