According to CarMD.com, a faulty oxygen sensor is the most common reason for that check-engine light to pop up on the dashboard. The fix could be as simple as changing out a dirty air filter, but you could also be on the hook for a $259.30 (on average) sensor replacement.
Some folks push the envelope on maintenance visits or ignore the manufacturer guidelines entirely. They think that’s frugal, but it isn’t.
The oxygen sensor is a good example. Sure, you’ll save almost $260 by not fixing it. But you’ll pay for it in other ways. Expensive ways.