My 2001 Xterra (313K) failed smog in CA for the first time because O2 sensor was "not ready". I believe this is related to a combination of a new battery installation and very little driving afterwards over the last 12 months (< 1800 mi). The test station suggested that I drive as much as possible before they retest, and I've been driving at least 1 hour every day both fwy and in town. I have an OBDII scanner, but when I scan the emission test readiness codes they all come up as "N/A" (not applicable). I don't know if this is a problem with the scanner or if these codes simply aren't available on 2001 Xterra's. Has anyone here been able to see the emission readiness codes on a 2001 Xterra with any kind of scanner? Thanks.