Power locks continually clicking while driving

"BCM" is the "body control module", or "body computer". The engineers are not able to do any of the things cars did for decades without adding an unnecessary, complicated, unreliable computer today. Those computers cause a lot more problems than they solve.

Given the description of the symptoms, the first thing I would suspect are broken and frayed wires between the driver's door hinges. Inspect those first, then, if they are okay, your mechanic can use a scanner to see what the various computers are seeing. For example, if the body computer is commanding the doors to lock, if the "lock request" command is showing up, that would point to wires in the door hinges rubbing and shorting together, or corrosion between the switch's contacts. If no "lock" command is showing up but the computer is trying to lock the doors anyway, that is the time to suspect the computer.

Other inputs will be shown on the scanner too. A lot of GM vehicles are programmed to lock the doors when you shift out of "park", and to unlock automatically so the bad guys can jump in when you shift into "park". The computer could be getting erratic signals from the transmission range switch.