TSB: Chevrolet Camaro MIL, Exhaust Noise

This bulletin applies to 2016-2024 Chevy Camaro vehicles equipped with an LGX, LT1 or LT4 engine. The check engine light may be on, accompanied by an exhaust noise. DTC P12FD or P12F0 may be set.
The concern may be caused by an exhaust actuator that was installed but the learn procedure was not completed. Some vehicles are equipped with passive exhaust valves (PEVs) that are purely mechanical in nature. They are spring operated and they are not able to be externally controlled. 
The correction involves a relearn of the cylinder deactivation valves using GDS2. These valves are also referred to as the active fuel management (AFM)  valves, and are located before the muffler. Do not replace any parts for this concern.