2007 Dodge Caravan only runs for 3 seconds

My caravan when started only runs for about 3seconds. When you turn it off and try to restart may not do anything. If you let it sit for a time it will start and run for 3 seconds. If you try to start it to soon the tach will show rpms even though the engine is not running. Any ideas.?

Are you using a new key? It sounds like the vehicle is being started with a key that the security system doesn’t recognize or isn’t programmed to the vehicle. The engine will shut off after 2 seconds when that’s the case. Check out pages 15 & 16 of the owners manual.