can you tell if an o2 sensor is bad just by looking at it? Im constantly throwing code 45 and im thinking the sensor in my header went bad.

 

No.

How many miles are on this O2? If you were running rich for a length of time (like an untuned basemap), you can foul out the O2 sensor. Burned coolant and oil will also conataminate an O2. O2's are serviceable items anyway, they do have a finite life span. On my stock 99 hatch, I typically see a decrease in performance/gas mileage at around the 60-70k mile mark....and this is a stock Y7 ECU that always leaves the spark plugs a white'ish/tan'ish color when I change them at the 15k mark (point is, its never seems to run rich).

 

99 si has about 99k on it now

when i changed the cat, the sensor looked a bit on the black side. I havent checked the one on the header recently.