My check engine light came on and the code was for one front O2 sensor. I reset the code and ordered two sensors. While driving a couple of weeks later the CEL went out. Then about three hundred miles later the light went out on its own, and hasen't come back on for approx 1000 miles. WTF is the deal with O2 sensors and the CEL?

I now have two front sensors waiting to install, but don't want to do it if it is not necessary. I kw with 118,000 miles it will surely be necessary pretty soon, but it is winter and my garage is cold.

What is the deal with the on and off lights???

 

Intermittent problem. Pull the codes (there will probably be some stored even if the light is off) and start diagnosing from there.

 

I get 05/05. That indicates no problems. I won't argue with the ECU box, but come spring I will still change out both O2 sensors, seeing how I already bought them.

I should also note that the engine seems to be running fine and on the last take of fuel I got over 400 miles. That was with a ski rack during sub zero temps going over a 9600 ft pass and all other miles being put on at 5300 ft to 7500 ft elevation. Not bad for a 95 with 118,000.