2005 Trailblazer won't start.?

I got up yesterday morning and my trailblazer would not turn over. It cranks but won't start. The dashboard shows the engine down symbol. I ran diagnostic on it and it indicated throttle possition sensor. I changed out the throttle body all together w/ new ac delco parts. Still won't start. Checked pressure from fuel pump and seems o.k. Battery is charged and fine. HELP!!!