2008 Yaris starts but won't run

[Ashton]

I haven't been able to figure this one out yet. My Yaris starts instantly. Just like it should. But the instant you let the key go back to run, it shuts off. I can hold the key in the start position and it continues to run. I can rev it up. But, the starter doesn't like that.
I'm thinking it's a relay somewhere? I don't know which one to check. Anybody have any ideas?
Ashton

[zoidberg444]

I'd almost wonder about something being wrong in the ignition switch. Evidently you are losing a circuit to something important like fuel, injectors or ignition coils.

[Brighton]

+1 to worn out ignition switch

[Ashton]

I replaced the ignition switch. No change.

[ex-x-fire]

You need a wiring diagram.