Codes 21,22,23 all showed up at the same time. Voltage across battery (engine running) was below 12.6volts. Interstate MTP Battery was new.
Inspected the voltage regulator (back of alternator), the bushing were worn down. The VR was replaced. After VR was replaced, voltage across battery (engine running) was at 13.8volts. Codes were cleared. It's been 6 months , no codes 21,22,23.

Used Voltmeter to test voltage.

Hope this helps.