My 91 has a check engine light on and traction light on and I ran codes and it comes up with an o2 sensor. The odd thing is that after driving the car for about 15mins both lights go out and soon as you as shut the engine off it comes back on again. Is it as simple as an o2 sensor or is there more to it?
Thanks

 

You might have a "lazy" o2 sensor

 

Probably the problem.
I vote O2 sensor.

 

First off all, what's the code number?

 

Thanks guys for the response. I did the check engine 3 weeks ago and don't remember but will check it again today as soon I get my car back. I do think it was the o2 sensor error but I want to be 100%

 

the OBD-II error code number is important in 95 and up models, as there are two pre-cat and two post-cat O2 sensors - the pre-cat ones are actually important for how the car runs and your fuel mileage, whereas the post-cat sensors are really just kind of emissions "tattletales" for municipal air quality testing stations and could be ignored if you don't live in an area requiring emissions testing and don't care about clean air.

however, yours being a '91, (OBD-I) I think you just have a total of 3 sensors rather than 4 (one pre-cat and two post-cat)