My 2001 MT has around 97K on it and recently the CEL came on. I have a OBDII reader, and it is the P1164 code. I have reset it, but it comes back on. In an earlier thread, I was told that around 100K, the 02 sensor should be replaced and I am wondering if this is something I can do myself or if a trip to a dealer is necessary? I should say that I haven't noticed any performance issues and the light came on right after I filled the gas tank.