4 cylinder engines normally have 2 sensors, 1 before the cat and one either in the cat or behind the cat, sensor 1 I is before, sensor 2 is after. 6 an eight cylinder engines have three on a y pipe exhaust system, and four on an H pipe exhaust system. Sensor 2 is ALWAYS AFTER the cat. The banks are the confusing part, and it is by maker of the car, but if you look at your valve covers, one is slightly forward of the other one, and is bank one. Bank one's first spark plug is at cylinder one!
Saturday, February 13th, 2010 AT 8:29 AM