240sx Check engine light gas?

[pndjones]

Hey guys I dont know if any of you guys have ever heard of this but... I just bought a 1995 240sx 2 weeks ago and it is bone stock. When i got it, it had a full tank of gas. Last week and burnt that off and got more gas. I put in 87 octane and the check engine light came on about 5 miles later. I looked up the code and it said that it was a knock sensor. Hoping it was nothing serious and was just bad gas, I cleared the code and hoped to never see it again. Well, I just filled up again a couple days ago this time on 93 octane and the light came back on. I have not read it yet but I think it will be the same thing. I will post an update tomorrow when I read the code, but I Just wanted to check with you guys and find out if anyone had the same problem, know what it is or know how to fix it. Thanks