2009 DTS "Battery Saver Mode" activated?
 

Hello, new member to the forum! My first Cadillac had been a dream come true until last week. One rainy night, the battery light came on with "service battery charging system." It was intermittent and then it became "battery saver active." Immediately took it to a shop the next morning. No issues. Both the alternator and the battery checked out. No corrosion on the terminals. Couldn't repeat it. Nothing again for several days. Then yesterday, another rainy afternoon, it happened again. If it's not battery or alternator could this be something as simple as a fuse, or possibly something so small that is secretly draining my battery overnight despite locking my car every night. Something so small that nearly drains my battery overnight that I get a warning light and battery saver active the next morning. Anybody else experienced this on late 2000s models? Does it have anything to do with outdoor moisture? Much appreciated.