Is it possible for my o2 sensors to already be bad if my car has only 52k on it? My engine light came on and I went to Autozone and they check it with there little diagnosis tool and it said that one or two of my sensors were bad? I am not experiencing any symptoms of bad o2 like crappy gas mileage, detination, pinging, or any thing. Just wondering if there was an issue of defective o2 sensors from the factory on the 99 Maxima GXE's? Thanx