Cadillac CTS First Generation Forum - 2003 - 2007 Discussion, Rear Left Door Ajar in Cadillac CTS Coupe, Sport Sedan and Sport Wagon Forums; I get this message when I put the car in drive. (REAR LEFT DOOR AJAR) I assume its a sensor ...
The "door ajar" and "door open" switches are integrated into the lock actuator which is part of the door lock assembly.
You could have a bad switch or a wiring issue that is making the computer think the door is open.
The door will have to come apart for diagnosis and testing, also a scan tool might be required to pinpoint which switch is acting up.