Code 1222 - 535i

Did you put in a NEW sensor, or the one you found at a junk yard?

If new, was it the type that simply plugs in, or did you have to splice the wires? If you spliced the wires, did you connect them properly or reverse them? If you spliced them properly, did you make sure you had a good connection, or is the splice job leaving something to be desired?

There are far too many questions for you to answer. Since 1222 essentially means there is a malfunciton and makes no reference as to if the trouble is a lean or rich mixture, then you have to sort out vacuum leaks that will cause a lean mixture, and pressure regulator issues that can cause a rich one.