Common reason for CEL to come on?

o2 sensor?

came on in my GF's 01 civic last week just haven't had a chance to take it over to advance to have the code spit out yet.

 

It could be anything from a misfire, sensor malfunction to not screwing your gas cap back on properly.

Does it drive any different? is it bogging down? trying to stall out? sputtering?

 

nope, no sputtering, no stalling, nothing. She had the tranny replaced under the extended warranty one year ago. I'm just looking for anyone with common reasons as to why the light would be thrown on. Checked her gas cap, drove her car around this weekend, changed her brakes for her this past weekend. I'm going to stop by advance auto this thurs when im off from work to had the code retrieved.
I did notice on Saturday when i was changing her front brakes for her that one of the sway bar links on the pass. side, the small cap on the end had popped off, so i popped it back on. other than that, it's great.

Oh well, I'll find out the whole truth later this week.

Chris