Cars voltage is too high after alternator replacement

Hey everyone! I have a 2006 Jaguar X-Type, 3.0 Litre that is reading at 15.2 volts when the car is on. 12.5 volts when off (the battery is good)

I just replaced the alternator with a brand new one, so I don't want to believe its faulty (The replacement sucked so much). Is there any other troubleshooting I can do for high voltage besides replacing it again? Its causing transmission issues with the TCM