02 Sensor location identification
 

Does anyone know which sensors are which as far as Banks and sensors?? I have been getting a P0420 and a P0133 on a 96' Ford Explorer. According to the error code....P0133 is "02 sensor circuit slow response (bank 1 sensor 1) ". Which one is bank 1 sensor 1? I have searched here and have saw post saying "post the code and we will tell you which sensor is bad", but nothing really saying which is which. I have replaced 2 of them that were easy to get to, but unfortunately that did not help. The other 2 look like they will be hard to get at, and I would rather not guess. Does anyone know which one this is??

Thanks,

Bob

Bob, bank 1 is the passenger side. Sensor 1 is the one closest to the exhaust manifold, and screwed into the header pipe. It looks to be relatively easy to access from underneath.