Chevrolet Sonic Owner's Manual: Automatic Door Locks
The vehicle is programmed so that when the doors are closed, the ignition is on, and the shift lever is moved out of P (Park) for automatic transmissions, or when the vehicle speed is above 13 km/h (8 mph) for manual transmissions, the doors and the trunk/liftgate will lock.
To unlock the doors and the trunk/ liftgate press on the center stack or the driver door
If equipped with an automatic transmission the vehicle must be in P (Park).
If equipped with a manual transmission the vehicle must be in Neutral with the parking brake set.
This feature can be programmed. See Vehicle Personalization.