The headlamps and parking lamps are activated 15 seconds after the windshield wipers are turned on.
For this feature to work, automatic lighting must be enabled. See Headlamps for additional information.
When the ignition is turned off, the wiper-activated headlamps will immediately turn off. They also turn off 15 seconds after the windshield wiper control is turned off.
Chevrolet Cobalt Owners Manual. Shifting Into Park (Automatic Transmission)
WARNING:
It can be dangerous to get out of the vehicle if the
shift lever is not fully in P (Park) with the parking
brake firmly set. The vehicle can roll. If you have
left the engine running, the vehicle can move
suddenly. You or others could be injured. To be
sure the vehicle will not move, ...