RepairPal Certified shops can diagnose and repair your 2009 Cadillac STS. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
Hello,
The linkage from the door handle to the latch is broken or loose, or the handle itself has an issue.
To find out what is going on, just remove the door panel (carfully!!), and have a look. It will be very obvious.