Car has been operating w/o issue until I recently lost the keys to the Saturn Vue so ordered new ignition switch assembly. Swapped out the assembly and now the car starts up and runs for 2-3 seconds and stops. The battery is fully charged, so no issue there. I looked on line and see that it may be a Mass Air Flow Sensor or EGR Valve. Need to know if anyone else has had this issue.

Many thanks.

 

You need to perform a passlock security system relearn.
The ignition switch has a passlock sensor in it. This needs to be synced with the body control module (BCM) within which the security system resides.

Perform the procedure at the link below exactly as it is written. You will run your battery dead if you do not hook up either a charger or jumper cables to a running vehicle as the procedure takes 30 minutes with the key in the on position.

Passlock security system relearn procedure