I have an Altima 97 with 19k miles on. Recently, the yellow engine light came on. I borrowed an electronic code reader which indicated that there was a problem with an oxygen sensor. Then the light went out by itself, so I thought this was just a glitch, but it came back on. Any ideas what this may be caused by? If it is indeed an oxygen sensor, is it something I can fix myself or do I need to take it to a shop? BTW, I don't know if this is relevant, but the car passed the smog check a few months ago.
Thanks,
A