I have a 2002 Accord EX (4-Cyl). Recently the CEL came on. I'm told this probably means the oxygen sensor needs to be replaced.

I have a few questions:
1. What is the worst that can happen if I don't replace the sensor right away?

2. How can I turn the light off?

 

there should be a code if the CEL comes on.

worst case scenario, car doenst run efficiently.

not sure how long resetting the CEL would last, since you'll be throwing the code until it gets fixed i believe.

 

How inefficiently are we talking? Lose a couple MPG or something more serious?