Hi,
I am driving a 2003 Honda Accord, Sedan, 4 cylinder. I have put on apprx. 28K miles which is not too much for an '03 year model. A week ago, one of the light was on. I did go to check at one Honda Car Dealer and the guy told me it was the 02 Sensor needed to be replaced. And he told me it will cost $500. I am not sure how important the 02 sensor is or whether I really need to replace it immediately.

1) What could go wrong if I don't replace it in time?
2)or what possibly endangers me while I am driving with this condition?

Anyone can help me to answer these questions. If I need to replace it then
3) Where I can get the lowest cost for the O2 Sensor replacement?
4) And is the $500 estimation reasonable?

Thank you,

Nqt--

I can't answer your questions, but just a word of warning:

Original parts are ALWAYS more expensive! Sometimes up to 2x the price, minimum!

Here's how to do it yourself:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-46563.html#post223376