makes me think you have a corrosion issue with the battery connections or cables.
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check all battery connections/cables. corrosion free, secure. neg/pos. pos all the way down to the starter.
batteries, alts, starters, once removed can be bench tested at most any auto parts store for free.
this also has a neutral/starter safety detent system. manual trans has a switch at the top of the clutch pedal. auto trans uses the range selector switch on the trans for that function. both (app) complete the starter circuit.
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FYI,
the reason it dies after starting from inder the vehicle is due to the anti theft system. not part of the security system (app). the computer senses a starting condition outside the ignition circuit. computer senses via resistance, and justly so, it's being "hot wired". fuel is cut by the computer seconds after starting in that scenario. actually severing power to the EFI circuit.
work around,
to get around that, if the ignition switch has an issue in the starter circuit terminal, you need to have a single throw *momentary* toggle switch sourced off the "ign" fuse going all the way down to the starter soleniod. hold toggle on, turn key to start position, release toggle and ignition switch (to "on" position). she'll stay running that way.
And we're supposed to guess the year, make, model, and engine, right? Just because you think every vehicle is wired exactly the same way?
Maybe the alternator is bad, or the starter.
Does it have a security system?
