There are four O2 sensors on the 3.7 liter V6 . Right bank and left . The right and left exhaust pipes will have an O2 before each catalytic converter and each side will have two after the catalytic converter as well. They are referred to as upstream and downstream , up being closer to ehhaust manifold and down being after the catalytic converter. The right side exhaust is referred to as right bank , conversely , the left is left bank. For example ; right bank upstream refers to the O2 closest to the exhaust manifold before catalytic converter on the right side exhaust. They all carry a separate part number since the wire leads are of different length . Pay close attention to scan tool readings when referring to up or down stream right or left bank . Optimally , they are changed in pairs or as a set if the down stream O2 sensors are found to be out of specification. DO NOT buy the cheapest brand you can find . NGK is chrysler friendly. We have had MANY a thread over poor parts replacement and headaches due to driveability problems due to CHEAP parts installed. Get the right parts numbers for the O2 your replacing and the best quality if replacing one at a time of the scan readings show one lazier than another but change in pairs is recommended.