98 civic, have the engine check light on.

had it scanned at the local auto shop, said it was o2 sensor bank one.

question: does this mean faulty cat? or is it the sensor, if its the sensor, then which one, i saw two.....

 

No, like the code says, it means you have a bad O2 sensor....

I'm pretty sure that Bank 1 refers to the upper one closest to the head, but I'm sure someone can confirm this one better than me.

 

What is the code number? Bank 1, sensor 1 is the first sensor and bank 1, sensor 2 is the second one. There is no bank 2 on a Civic (this is in the OBD standard for V6 or V8 engines that have sensors on both manifolds).