Joe Padavano is correct in what he said here. If the scanner wont power up then someone clipped the 12 volt + wire in the OBDII ALDL pin #16. That will keep the scanner from powering up. The check engine bulb probably has been removed.
Be sure ALL the fuses are good .
You need to adress the engine / pcm communication problem first as you need that to read codes , live data and possibly to perform bi directional testing etc. in order to diagnose the problem correctly and quickly
Or you could spend a buttload of cash just throwing parts at it ,so you then can take it to a mechanic and complain you dont have any money to pay him to fix it.