Intermittent starting issues. Checked fuel system and nothing is wrong with it.

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I have a 2003 Silverado 1500 HD with a little over 100K miles on it. It is having intermittent starting problems. Checked the fuel lines/pressure, so it has nothing to do with the fuel system. It will crank, turn over, then die. I have talked to countless people and no one has any idea what it is. Took it to Advance Auto and checked the computer for codes, nothing, not even a check engine light. The only thing I haven't ruled out is the PCM going out or a sensor.