It appears there is a possible new issue vexing the ATS 2.0T with the manual transmission.
As you might recall, initial reviews of the ATS largely raved about the car’s handling but panned the manual transmission’s feel. These reports sent Cadillac back to the drawing board for bushing and shifter calibration to the point of ATS manuals being unavailable during the initial weeks of sales.
Now, it appears the cars have an engine computer glitch that causes cars to unexpectedly stall in neutral or with the clutch depressed.
This is apparently corrected with a recently released software fix, but hasn’t yet made it to recall status.
If you are having stalling issues with your manual ATS, get thee to your dealer ASAP before you find yourself stuck at a light with a non-running car.