I went to the nissan dealer to get my maxima checked out because the service engine light came on last night and i kept overhearing the service guy tell about 3 or 4 diff customers that they need a new oxygen sensor .I wonder if these sensors are defective or something i mean i heard 4 people being told these things are bad and i always see message in this forum about o2 sensors biting the dust

 

I'm not sure exactly what you're asking, so...
1) O2 sensors go bad. It's not a permanent part, it's like a spark plug.

or,

2) Are you asking whether they are of poor quality?

 

There is a service bulletin about 96 Maxima O2 sensors.

 

service bulletin, as in, it's a warning problem on the car.
Or as in, you can take the car in and they will fix it for you?

isn't there one bulletin that makes car makers fix a problem for free... and ones a warning for the car? I can't remember damn!

 

I wonder if that is why my car is running lean. I checked the spark plugs yesterday and the tips were whitish. I'm thinking it's either the Mass Air Flow sensor or the o2 sensors....