Hi! I need some information regarding my O2 sensor. I have a 1998 nissan 200sx with aftermarket header and muffler and my check engine light is on. The code claims the second O2 sensor is bad. I would like to know how many O2 sensors are on this car and where they are located. My car has one sensor in the header and another after the catalytic converter with a long harness. I am not sure if this was moved as there is an adapter for a pre-cat sensor. I need to know where the second sensor should be so that I can buy one and get it replaced. Thanks!