In December, while I was on the freeway returning from my mother's house, the "check engine" light flashed on. I bought a scan tool, which told me the problem was "P0133, O2 sensor circuit slow response, Bank 1, Sensor 1."

I take it that there are two oxygen sensors, one in front and one behind the catalytic convertor, and that this is probably signaling a problem with the front sensor.

I tried clearing the code about a week ago, and the "check engine" light has stayed off in daily driving in a mixture of city and freeway driving. I'm thinking that:

1. The problem was a transient one and hasn't recurred, or the light would have come on.
2. The problem is a sign that the sensor is on its way out, but not yet dead (and I might be able to get through until better weather, since I don't have a garage).

Am I understanding how this system works?

Good to know I may not need to drop big dollars on the problem right now.

I agree - if a code doesn't have the common decency to behave in a consistent fashion I don't worry about it.

I don't fully understand the system, but I can tell you that I have cleared many codes never to see them again. Just because you get a code, doesn't mean it is a permanent problem.

I had a dealer tell me I needed two O2 sensors and a new Cat conv. all at the tuen of 1500 bucks. I bought the scan tool cleared the codes. That was 40,000 miles and 3 years ago!!!!!