This isn't so much a question as it is a learning moment. A few months back my check engine light came on. I used the Blue Drive OMBD sensor and it gave me an P0441 error message. My mechanic quoted an expensive repair. I asked if I could continue to drive the car and was told I could, but it would have a negative impact on drivability and fuel economy. He was right about the fuel economy. Prior to the error message I averaged 430 miles per tank of gas. I was now averaging 389 miles per tank. A search of the Internet, and this message board, suggested the problem could be solved by changing the gas cap. Interesting. I noticed my gas cap was no longer clicking when I turned it, so it probably needed replacing. Unfortunately, after changing the gas cap, and clearing the error message, the message came back. I decided to live with the problem. Fast forward to this past Monday. My battery gave up the ghost. After replacing the battery something interesting happened. The check engine light was no longer on. I am back to near 430 miles per tank. I assume that disconnecting and reconnecting the battery reset the computer. I learned something new.