I don't have a check engine light but I've been thinking I should maybe replace my sensor(s) just to prevent any type of problems. The sensor before the cat was replaced about 2 years ago, the one after the cat has never been replaced. Looks like I can get them both for $177 here:
My question is: are these the correct one's and is Denso a good brand to buy?
2nd question: Will replacing the rear one do anything, or should I replace both?