o2 sensor code - 89 century

[89_Century]

Drive a 89 century, 3.3. I recently got a check engine light while driving home... It stayed on for less than 60 seconds and then went off and I have not seen it again. I checked the stored code and it was a #13 - o2 sensor. I have reason to believe the problem may be with the ECM itself and not the sensor. So my question is: Will the CEL come on everytime the ECM detects an o2 fault? Or will it not come on anymore when it sees a #13 since the code is still stored in the ECM? Thanks.

[maxwedge]

It will come on again and the ecm is almost guaranteed not to be the problem.

[89_Century]

Thanks - some of the other reasons I had suspected the ECM: In the past two weeks, twice has my odometer started to spin backwards while driving. Once I was able to bang the dash to stop it and the other time I had pull over and turn off the car. Not sure if this was a mechanical or electrical problem. Also, my fuel gauge needle seems to be fluctuate more than usual due to acceleration and deceleration. I suppose this could be due to the sending unit though. Any other thoughts? Thanks.

[maxwedge]

If you can change the speedo issue by hitting the dash top, the pcm is not an issue here. 02 is cheap about 25$ on that car and it is 16 years old!