Have Ford Questions? Ask a Mechanic for Answers ASAP
Hello and thank you for your question,If you scan the computer system are the any fault codes setting?Fluid level is clean and full correct?
Okay well if there is no pressure from the pump and the torque converter is turning it and the selector level is moving into the proper gear selection at the transmission then the problem is likely a failing pump or an internal leak in the transmission . The computer system on this transmission can not command neutral and if there was an electronic control issue you would usually have a fault code and or codes.
Start with making sure the shiftier is moving at the transmission and if so then there really is no way to check the pump besides checking the pressure with out removing it . Did you make sure the torque converter was properly seated when you installed the engine?
If the converter is not turning the pump there would be no pressure . One big problem you have is you dont know what condition the transmission was in before you did your overhaul. You may just have a failed transmission.
The code P1506 is an IAC (idle air control valve) concern and will have no affect on the transmission. See the link below.https://dl.dropboxusercontent.com/u/104923897/P1506%20Jul%2020.pdf
Okay that can only mean the pump is not producing any pressure or theirs an internal issue causing a lack of pressure. I do not think this is anything you caused and your likely looking at a replacement and or an overhaul.