On vehicles with power door locks, the doors automatically lock when the shift lever is moved out of (P) Park for a vehicle with an automatic transmission.
For a vehicle with a manual transmission, the speed must be greater than 5 mph (8 km/h).
The automatic door locking feature cannot be disabled.
Chevrolet Cobalt Service & Repair Manual. Door Handle
Exterior
Front
1.
Remove front door trim panel as outlined
in "Door Trim Panel."
2.
Remove front door water deflector.
3.
Remove three front door handle retaining
screws, Fig. 1.
...