I changed engines in our 03 intrepid and then it will not start p0057 code

no the engine is an 01 and had to change a whole bunch of things like the whole wiring harness for the engine and the knock sensor, crank sensor,cam sensor upper intake and so on. I read somewhere today that i may have to change the gear on the cam that the cam sensor reads. Have you heard of this?

POO57 = O2 sensor heater circit, not your no start problem! Do you have ignition spark and fuel to the plugs?

yes and evry once in a while it backfires like it is out of time so thats why i was wondering if you have ever heard of having to chance the readout wheel on the cam. but it has the transmission and the engine that were together in the 01