Hey, I recently had a code for knock sensor,

I got it replaced and yes I had the battery unhooked, when I did it all. Was an oem knock sensor. Well now when I go to start the car the code comes back immediately. I clear it, it says failed to clear code. Then if I drive the car a mile, clear the code it goes away, but then when I start the car it comes right back! I’m so confused what is Making it come back immediately.. it’s making my car run like **** and use a lot of fuel and running really hot on the second o2 sensor.. any input is greatly appreciated thanks!