So I’ve had my 07 cobalt ss/sc since 2007. It’s always run great, just O2 sensors are always garbage. So the last time the rear O2 sensor blew, I said f*** it I’m not replacing it until it starts running differently. That was 2 years ago. I’ve periodically checked the check engine light to make sure no other codes came up, and they never did. Just the sensor. My gas mileage hangs around 33-35mpg. My car has 185k on it, everything is OEM. I will need to replace the timing chain soon since I haven’t yet and I worry about it, even though the car has not indicated any issues or reason to be concerned. I have stopped driving it often as of 5 months ago. I used to drive it daily, now I drive it maybe once a week and just in town, which is rural. Otherwise, nothing is wrong with the car.

today, after 2 years, my check engine light has just turned off. I didn’t replace anything, I did not buy a new sensor. It runs the same. I haven’t even changed my oil or done any other maintenance recently. My husband said if it’s off great! But this concerns me because nothing has changed in the last 1 year for it to just go off. I can’t help but have an impending doom feeling that suddenly something awful is going to happen to it. I can’t get it looked at til Monday of next week, not even for an OBD check.

Are there any other reasons the check engine light would just turn itself off that don’t include fixing the problem?

thanks in advance and sorry if this is a stupid question!