You need to have the downstream oxygen sensor replaced. Your oxygen sensors monitor the air/fuel ratio your engine is burning and adjusts various components of the engine according to that reading to make it run as smoothly as possible . A lot of times you will get a code and not notice a difference but sometimes they’ll cause rough idle , stalling , poor performance , bad gas mileage etc . It is threaded into your exhaust after the catalytic converter . What year Jeep and what engine do you have ?