A trouble or error code of P1151 on a Ford Expedition indicates an overheated exhaust oxygen sensor. This may occur because of a problem in the sensor or a problem in another system that overheats the sensor.
A leaking exhaust system, an electrical problem or problems with the fuel system are all possible causes of the P1151 error code. None of these areas are likely to prevent the car from driving properly in the short term. Diagnosis by an experienced mechanic is the best way for Ford Expedition owners to figure out the exact nature of the problem. Ford Expeditions manufactured between 1997 and 1999 have a known issue with an airflow sensor that sometimes causes a P1151 code.