Pontiac Repair: 1999 Pontiac Montana 3400, passkey iii, pontiac montana

Question
My van starts and runs for about 3 seconds and then dies.  Pass key light flashes on and off all the time.

Answer
Hi
I would suspect the Passkey III sensor.
It MAY be the ECM, but more than likely, it is the passkey sensor.
You MAY have a non passkey III key, if key is new, and need a passIII key.
The key should have a PKIII engraved on the shank, just where the black plastic cover is.
I hope this helps.
Pawl