I too have a 2017 Bolt, and it is making a strange clicking or tapping noise when I enter the vehicle. The noise generally stops when I press the brake pedal. When it started, it would click 5-6 times. Now it is up to 30+ times (tap-tap-tap-tap..). I have even had times where it starts tapping when I shut the car off.
I already know it is the iBooster. GM was unable to diagnose it the first time but I have a really nice video recording of it clicking and I had the hood up so I could feel around the brake cylinder and assembly and it was certainly coming from there. A wise individual on the Bolt FB page suggested it was the iBooster earlier.
Anyway, just wanted to post here so others knew the tap-tap-tap is a thing, and the iBooster is clearly marked with a label and bar code beside the brake master cylinder. Car goes in on Monday to a different dealer, and hopefully we can get that taken care of.
email me at
[email protected] if you want a video recording of the sound from inside and under the hood of the car.