Ford Repair: 1997 ford expedition xlt with 4.6l triton engine, ford expedition xlt, haynes manual

Question
According to the sensor codes, my truck has a fault in the downstream heated oxygen sensor and missfiring on cylinders 2 and 6. I would like to know if the cylinder problem is caused by the sensor or vice versa. I have a haynes manual which helps. however, I'm not adept at cylinder problems. The engine in this truck was recently replaced. About a month ago. Could the head gaskets be bad already?

Answer
Hello and thanks for the question...I'll try to help.
 The sensors usually don't CAUSE the problem, especially on just two cylinders.....I would take a look at the tune up condition of the engine........replace the spark plugs and or ignition wires, reset the fault codes, and go from there.
Hope this helps,
Erik