[AllanC]

. . . . Now it'll start and stay running as long as I hold the key in the start position, but dies right after I let it return to the run position. I just changed the ignition switch (not the lock). . . . .

Does your vehicle have the remote start feature on the key fob? If YES can you execute a remote start and the engine will stay running?

 

[AllanC]

. . . . I rechecked the fuses. And the little rectangular box right next to it. I assume those are ignition relays or something. And then tried to test power to the coils. All of which involved disconnecting and reconnecting the various parts. Then it started and ran for 10-15 minutes. . . . . .

Here is an image of the relays in the TIPM and fuse box. Note the ASD / main relay. When the ignition key is turned to RUN and then START, a signal is sent to the TIPM to engage the starter. The TIPM energizes the ASD / main relay and the starter relay. I am thinking that there is corrosion either on the internal contacts of the ASD / main relay or corrosion / burned pins on the relay and / or mating receptacles.

For a quick test swap the ASD / main relay for the radiator fan relay. Run the engine and see if it shuts down after a short period of time. If engine does NOT stop then you have found the problem. Check relay and pins and receptacles in the socket.