How to read an oxygen sensor
 

Hey guys, I pulled my O2 sensor out after 70K miles on it. The sensor was completely white except for a little black scar. What does it mean? Is my engine in good condition?

I think the best way to tell is to get a digital meter and put one lead on ground and the other up the backside of the 02 sensor wire at the back of ECU. Then go for a drive and observe the meter. Just looking at it does no good. It could look like that and the wire having been broken for two years. Looks good though.