CEL came on yesterday, ran the code, bank 1 sensor 1 O2 sensor, im pretty sure that its driver side before cat. But is that considered upstream or down? Or is it either at all? Any specific brand/model to use? Also a question with passenger brake light; replaced 2 time in last 18 months and just went out again. Plug looks fine but not sure why this keeps happening. Again i really hate to do a new post but getting pretty frustrated trying to find.