Why won't my 04 dodge ram start. It seems there is juice to the starter

P0522 = oil pressure circuit low, which can be sensor or wiring related. It could also be that your engine is locked up. Have you tried to turn your engine with a breaker bar / socket?

IF you replaced the engine, then I imagine you may have a voltmeter and some other equipment and tools. FIRST have an assistant help you-- Test for battery voltage at the starter solenoid, while helper turns the key to the 'crank' position. IF no voltage at that time, diagnose that side of the circuit. IF there is correct voltage , diagnose either faulty GROUND circuit, or poor connection between battery and starter positive cable.