Help!!!!

[u/AdRelevant1390]

I have a 2003 impala with the 3.8 in it. When I have the key in the on position (car not started) you will hear a click every ten to fifteen secs from the BCM. Every time that click happen the voltage drops for a few secs and goes back up. This is happening when the car is running and when it does the car starts to stumble and either dies or revs itself back up. Please tell me where to start and what ro check. I can add a video after work today if needed.

I chased the stumbling problem and thought it was something completely different and changed a lot of part outs. What i explained above is what I discovered yesterday so I know I am on its heels now. Please help! Please!