Gas Recirculation Valve (egr Valve) problems of the 2014 Cadillac CTS

Vehicle displays �service rear axle� �service stabilitrak� �park assist temporarily unavailable� �automatic seatbelt tightening unavailable�. 4 separate and unique occurrences. Some have also included �reduced engine power�. Typically the messages come on and reduced power occurs after expressway driving, followed by stop and go city driving or traffic. Also ambient temps are over 80 degrees with each occurrence. Lastly engine bay is extremely hot after the service messages are displayed. Engine temperature gauge does not indicate overheating (displays under the halfway point of the gauge). I have 2 separate video documentations that can be uploaded to youtube. 1st occurrence resulted in cylinder head replacement under warranty. The next 3 occurrences have all happened after the warranty service. Dealership has been unable to replicate the issue after the car cools down. Cadillac customer service said a second dealership review was required even though the car was brought to the dealer with the above service messages present. Attached documents display first warranty service, and second record service messages being present. Similar TSB issued for the ats-v lf4 engine for �service rear axle� or �rear axle off�, also the lt4 engine has a TSB for engine overheating and going into reduced power mode when the charge air cooling system is not refilled properly via vac-n-fill method. This vehicle has a similar liquid to air, charge air cooling system, requiring the same type of fill method. Full disclosure I am a general motors employee.