Hello again CEG. It finally happened to me today. My first CEL. After searching, I have found that code P1131 means O2 Sensor Bank 1. Could someone tell me whether or not I am exactly right before I go out and buy the sensor so that i can replace it? Also, is this specific sensor hard to replace? What tools will i need? I ran across all of this stuff when I was searching but couldnt figure out which sensor was the hardest to replace. Thank you guys.