I had that code, and it was an O2 sensor

Obviously your results may be different, but when I was at ND my car started getting half the gas mileage it used it. Went from ~400 miles a tank to ~250. Also was accelerating a lot slower. I took it to AutoZone and they ran the codes for free, and that's what it was. I remember because it was a pain in the ass to find a mechanic who would work on it in South Bend (It was a 10 year old Audi - not my smartest purchase, but still the most fun car I've owned. I don't own any, now).

But yeah, it was the O2 sensor that had gone bad. According to the guy who fixed it, that resulted in an incorrect mix of fuel and oxygen in the engine, or something like that, which caused the gas mileage to plummet. I know nothing about cars. Ended up costing me a couple hundred bucks.