Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
The voltage reading at the cigarette lighter isn't always indicative of what the engine is putting out on these newer vehicles. The voltage from the lighter is highly regulated by the PCM to avoid cooking your Iphone or any other accessory that might get plugged in there.
At the same time, it's perfectly normal for the alternator to only put out 12-13 volts while running if the battery has a full charge. It's a fuel efficiency thing- if the alternator isn't working full blast to put out 14.9 volts all the time then there is less load on the engine. Less load means better gas mileage.