Ignition problem

My son has a 3.8L automatic transmission. It won't start. We turned on the ignition and jumped the starter and it runs for about 5 seconds and then shuts off. All fuses, relays are good. There is no voltage on one of the inside fuses which is labeled PCM (crank). I believe maybe it isn't supposed to unless it is running? I suspect either the ignition switch or the PCM (very expensive dealer must program). I thought if it was the ignition, it should have stayed running with the ignition switch on by jumping the starter solenoid and it almost does! Help! He doesn't have the huge cost this will be if it goes to the dealer (it won't!). Thank You for any help.