Q: Engine light on and vehicle running poorly.

The symptoms your CTS is experiencing are symptoms I have seen often in prior Cadillacs. What I suspect is that your CTS is likely dealing with problems concerning the throttle body. The engine in your CTS is equipped with an electronic throttle body. If your Cadillac’s computer senses a problem with the throttle body or a problem with the attached sensors, then the TC light will illuminate with the a check engine light. Power will also be reduced and the vehicle will be made undrivable. Your Cadillac becomes undrivable in order to keep the engine safe from damage, caused by overheating. Along with the fact that the symptoms will likely be intermittent, the failed part could be the throttle body itself, one of the sensors attached to the throttle body, the connections to the throttle body or even a bad ground strap. Since there are so many possibilities, it is best to enlist the assistance of a certified mechanic to inspect why your car is losing power and displaying the check engine light. This is the quickest and safest way to get back on the road.