2G DTC P1500/Bad alternator?

[Tigerinstincts]

Would like confirmation and guidance that my alternator's rectifier is bad and hopefully not my ECU.

Recently picked up a P1500 code and when I went to check the voltage across the battery while the car is running, I'm reading anywhere from 13-17 volts. I immediately shut off the car and the next time I go to move it, the voltage across the battery reads 11.8 volts no matter what rpm I increase it to (tested up to 5.5k rpms).

Here is the testing I did while the car was running.
Voltage drop across battery's (+) terminal and alternator's (+) terminal: .01V
Voltage drop across battery's (-) terminal and alternator's frame (ground): .005V

Voltage at red wire on alternator's 4-pin harness: 11.8V
Voltage drop across battery's (+) terminal and alternator's red wire : .01V

Voltage at blk/ylw wire on alternator's 4-pin harness: 10.6V
Voltage drop across battery's (+) terminal and alternator's blk/ylw wire: .03V

Voltage at green wire on alternator's 4-pin harness: 4.6V
Voltage drop across green wire from pin 41 (ECU harness side) to the alternator's 4-pin harness: .001V

When I turn on my headlights and heater, the green wire's voltage does not drop or increase from 4.6V.
My battery dash light does not illuminate but seeing as I have 10.8V at the blk/ylw wire, I assume my alternator relay is completing that circuit.

Is this enough to determine if my alt is bad or a bad ECU through pin 41?