Battery and alternator is good. Voltage is still reading low 11.2. It has to be grounding or connection somewhere. Which wires/ grounding is a common problem where are they located.

 

Moved to C6 Tech for assistance.

 

In this order, alternator cable connects to battery cable at starter solenoid cable. From there, battery cable to engine fuse box terminal post, through fuse box to BCM on it connectors, out of BCM to ECM, and the dash voltage gauge/DIC reading, it telling the voltage at the ecm, not the voltage of the actual gauge cluster.
On ground side, battery to both chassis and to engine block just above the starter.

So tech 2 comes in handy, since you can pull all module voltages, to see if low BCM voltage with problems there and back up line, or if problem with BCM connector to ECM connectors or even ecm ground connector to chassis ground the problem instead.

As for under the hood, start motor with lights and HVAC off, use back terminal of alternator to pulll it voltage using the body of alternator as ground (should have 14.7+), then use battery ground and engine fuse box terminal to check for voltages, to make sure you still have 14.5+ volts. If yes, then problem is down line of engine fuse box.
If no and battery/engine fuse terminal reading is much lower, then check the starter solenoid terminal were the two cables connector to make sure nut is tight, and check the bolt for the battery to engine block just above the starter on the engine to make sure clean and tight as well.

 

Welcome to the C6 forum Josem. I see your first post this past April was concerning problems with the tail lights. Did you find a resolution to that problem? If yes, it would be helpful to all to post your results so the next owner can benefit from your experience. These cars are getting older and more problems are popping up as a result, so please close out and update your requests for assistance.

As to this latest issue, we need a bit more back story. What have you done that leads you to the conclusion that the alternator and battery are good and not contributing to your issue? This information on attempts for resolution will help us to understand better the scope of your problem(s). Dano has given you some good troubleshooting advice, based on the basic information provided.

Hope we can help you get this car fixed and on the road to enjoy it...GD

 

Welcome