With engine above 2000 rpm, charging voltage should be above 13.5V. The actual spec. is, with engine at 2500 rpm, 13.5 to 14.5.
The PCM adjusts setpoint lower in warmer ambient, higher in cooler ambient. So in summer, will be closer to 13.5V, in winter, will run closer to 14.5, but should always be between 13.5 and 14.5 at 2000 rpm or higher.
Ron - Years ago, it was suggested to have the dealer re-flash the PCM with certain problems, and that sometimes worked. I guess problem is that if it doesn't fix it, then you've paid for that, and then you've got to get another PCM anyway. I don't know what dealers are charging these days for re-flash.