I know this is a old post but I could not find a resolution. I have the same issue at cold start up. I started noticing this the last few cold start ups. It only last a few seconds and then goes away. The Camaro HW only has 1300 miles on the clock. I have added a video for the sound. Again only during cold starts when the engine has been setting overnight. The chirping/squeaking goes away after the car goings into closed loop.
https://youtu.be/_E_BAz2uYQk
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2018 Camaro 2SS M6 Hot Wheels,Edelbrock 2650, Hurst Short Throw Shifter. Production Number 90
1997 Camaro SS M6 LT4 tribute