Can you please describe what you mean by "Rear O2 Sensor"? The jeep straight sixes have a bank one which covers cyl 1,2&3 and a bank 2 which covers cyl 4,5 &6. Jeep often refers to Bank1Sensor 1 as the "Front sensor", and Bank 2 Sensor 1 as the "Rear sensor". ... Login to read more.