On a recent long trip the light came on. 1221. Seemed reasonable since it had been 100,000 miles from the last change.

Today the light went out. Stomp and still a 1221. Tried clearing with no luck.

Why would the CE light go out with a code in it? Is there some sort of mileage limit? That would seem kind of daft. It has been on a while (in terms of mileage--not time).

I will change the sensor, but am confused about the lack of the light (not to say that I am not grateful while driving at night).