Hello,

I drive a 2005 Toyota Matrix with 121,000 miles. Yesterday the check engine light came on when I was leaving the park. As soon as it came on my acceleration was greatly reduced. I could get to 60-80 mph but it was taking longer than expected. It acted like that for the rest of the day. This morning I went to get my haircut, the light was still on but it was driving normally. When I left the barber the light went off but I still went to Auto Zone to diagnose what the light was. The code P0328 came back which had to do with the knock sensor. The guy at auto zone was confused saying that that shouldn't cause problems. He said that I probably had bad gas and should use a higher octane. I don't know if I agree so I wanted to get a second opinion. Could it be the gas (I've been using the same gas with no problems) or do I simply need to replace the knock sensor or could it be something else. Should I try other things before replacing the knock sensor? Its driving normal now with no light but I don't think I should ignore this. 

Thanks