The vehicle has a battery saver feature designed to protect the vehicle's battery.
When any interior lamp is left on and the ignition is turned off, the battery rundown protection system automatically turns the lamp off after 20 minutes.
This prevents draining of the battery.
Chevrolet Cobalt Service & Repair Manual. General Motors Co.
FIG. NO.
BUICK:
EVAP System & Canister:
Century FWD
1
Century RWD
2
Electra FWD
3
...