^ Engine BANK
^ Up = Sensor 1 = Front = Closer to the exhaust manifold = Before the Catalyst
^ Down = Sensor 2 = Rear = After the Catalyst
^ Bank 1 is closer to the dash panel = RH (right hand)
^ Bank 2 is closer to the Radiator = LH (left hand)
The following O2 Sensor EXAMPLES show how to interpret the terminology:
^ B1/S1 = Bank 1/Sensor 1 = Dash Panel Side, BEFORE the catalyst
^ B2/S2 = Bank 2/Sensor 2 = Radiator Side, AFTER the catalyst
Per AllDataPro