I’m having issues with my 2003 Chevy Tahoe

What is your question?

When it snows or rains and I go to start my car the TC light comes on with a message of reduced engine power on the display if I shut it off and wait a minute it’ll start with no light or message. Then this weekend we took a long drive (which we never have done in this car) and then today we take it out and suddenly the engine idle is low and the car is dying at a stop or slower speeds. The shop says it’s the alternator but we had radio and no dimming headlights and this shop always says it’s the battery on every vehicle we bring in. I need help on what this could be?

What makes this problem better or worse?

It worse when it’s cold or wet out

How long has your 2003 Chevrolet Tahoe had this problem?

A few months started in fall with the TC thing