Service engine soon light has been on in my car for a few weeks. I have been ignoring it, but i finally made an appointment to have it checked out. The #2 O2 sensor where my y-pipe is failed. Nissan wants 230 plus tax to get it fixed. I just hit 40k miles and i have the 100k warrenty, but nissan of north america will not cover it. I am not sure if i should just buy an o2 sensor and do it myself, or just have the dealer fix it. I have had my y-pipe for about 25k miles. Anyone else have an O2 sensor fail?