Q: No Start on 2002 Hyundai XG350

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
Ok, I spent almost two weeks solid daily tracking everything with my volt meter from hood to ignition. I replaced a few parts however it still has no start. I replaced the ECU Relay and it started but would not drive-no power. The next day it would not start, same issues. I took it to the dealer and after them having it for three weeks we are leaning on the ECU.. How can you test it or pin test it if it isn't running or if the ECU is removed from the car? What are the directions to diagnosing the ECU for failure? The certified authorized hyundai dealer has stated they are stumped to find the real issue and do not know how to test the ECU? Can anyone help me help them????

(1) Answer
What is the reason the vehicle is not starting? Are the spark plugs firing? Does it have fuel pressure? Are the injectors opening?