Hi my girlfriend has 2009 g8 v6 with a battery light on ,I have changed the alternator , battery ,belts and checked connections. Everything tested good ,but yet the battery light will not go off. Is there something else I am missing, like a fuse or sensor that would keep that light on.
With only 1 post, its hard to guess what vendor components you put in the car. So I can only tell you to try this for now. Get the engineering page displayed on the DIC, and select battery voltage info. You should see a volt reading of something like 11.7 to 12.1 Start the car an see if the voltage reading ramps up to approx 14.7 in about 4 seconds. My battery icon remains illuminated until that voltage nears that 14 volt threshold point. If you put in a rebuilt or alternate sourced Alternator in that car (instead of a *new* GM OEM unit) you are almost guarantied to be in a peck of trouble (voltage output wise).
My alternator went bad at around 140k not long after installing an UD Pulley. It gave the Battery/Alternator warning periodically & eventually stayed on permanently. Autozone was the only place that had one locally. It was a Rebuilt unit that after installed the headlights flickered badly. Ended up returning & buying a used one *Normally wouldn't recommend* on ebay for 35$ shipped & it works perfectly! No more warnings on the DIC.
It's entirely possible that my used Alternator could be an Acdelco unit that's been rebuilt at least once in its lifetime. If memory serves me right it came from a car with 140k or so miles. Still way better than Autozone rebuilt garbage.