looking for the upstream o2 sensor on a 2008 civic si, I can't find any pictures, it's been raining outside so I haven't been able to work on it for the past few days. looked under the hood briefly but didn't find it. could it be under the car on the catalytic converter. I'd love to have a picture/diagram if anyone has one, thanks. Jeff

 

Yes it is at the front end of the converter.
Honda Automotive Parts
Part #16.

 

^^^yup but dont go buying a cheap sensuous only DENSO or NTK.