"SERVICE ENGINE SOON"

[Skimo100]

It happen again! Yesterday, I put gas and today the SES light came on again. Well, about a week or so ago I bought a code reader (ACTRON CP9180) and decided to to read the OBD codes. It turns out I get the P0326 code which says is a knock sensor. The gas that I put is BP (premium). I was previusly using the premium gas from COSTCO. Anyway, I did a reset and the SES light went out (off). I didn't hear the engine make any knocking noise nor the car felt rough when driven, at the time the light was on. And the light so far has not come on since I did the reset. My questions I guess are, can refueling cause the SES light to come on with a P0326 code generated from the OBD computer, even though I used always the correct fuel octane? And if I do have a bad knocking sensor, how come it doesn't come on after I do the reset? Knocking is the result of detonation, and detonation is caused by improper ignition of the fuel. Any idea guys why I'm I getting the P0326 code when I do the refueling?