Strange thing after replacing oxygen sensors (Page 1/1) Csjag AUG 24, 10:33 PM I recently replaced both oxygen sensors on my 2004 Chevy Venture van. I immediately noticed that the temperature gauge showed the engine to be running cooler. Anyone know why this would happen? Is there a connection between them and the radiator cooling fan? Fiero84Freak AUG 25, 08:23 PM This is because your vehicle is operating properly now. When you have a failing or failed 02 sensor, your engine accommodates and alters the fuel mixture. This often results in higher engine operating temperatures. This is why it's imperative when you have something like this fail you replace it immediately. Higher engine operating temperature, potentially combined with other issues like old coolant or issues that could cause overheating conditions, can quickly damage you engine.