02 impala alternator or body control module problem

I have an 02 impala with a 3.4L and 115K miles. Driving on a snow covered road all the interior lights (dash, radio, etc), exterior lights started intermittently flickering as the alternator warning light came on. It was not continuous. The exterior lights (including backup would flicker) even when the car was turned off for a couple minutes. When this happened it sounds like a relay if clicking on/off under the left side of the dash. The odd think is after starting the vehicle the next day, no problem until a few days later, this time on dry pavement. It will occur when driving or sitting still at a traffic light then be OK for a few minutes.

Since it was the original battery, I changed it but no improvement. I also ordered a new alternator given the mileage but that has not arrived (thinking could be internal regulator). I've also heard the impala and monte carlo have had body control module problems (BCM). Has anyone had similar problems that a BCM was the culprit? If so, where is the BCM located?

Thank you in advance for your help.