2012 Colorado No Crank, No Power, Multiple Fault Codes (P0685, P0013A, P0420) - PCM Issue Diagnosis

I own a 2012 Chevrolet Colorado 2.9L and am experiencing severe electrical and engine performance issues. The truck began acting erratically several weeks ago, with multiple diagnostic trouble codes appearing on the OBD2 scanner: P0685, P0420, P0013A, P171, and P0131. Initially, when I tried to clear these codes, the entire dashboard went dark—no interior or exterior lights, no instrument panel illumination—and the truck would not crank at all. The OBD2 scanner also stopped functioning during this event. I recently replaced both the battery and battery terminals, and inspected all fuses, ground connections (especially the fender-mounted ground near the fuse box), and wiring harnesses connecting to key modules including the TCM, PCM (below the TCM), and BCM (under the passenger kick panel). After these repairs, the truck started normally with no check engine light. However, during a test drive, it exhibited severe power loss—indicating 'low power' on the dash—and suddenly shut off while attempting to pull into my driveway. I was able to restart the vehicle only by keeping my foot on the gas pedal, which allowed me to move without stalling. Once stopped and parked, the engine would immediately die again. I re-scanned the system and found all original codes persisting—P0685, P0420, P-0013A, P171, P0131—and I cannot clear them. Additionally, for some time now, the dashboard has displayed repeated service messages: 'Service Stability Control,' 'Service STPM,' and 'ABS Light.' Given these symptoms—complete loss of power, no dash lights, no chimes, intermittent cranking issues, and persistent OBD2 codes—I suspect a failure in the Powertrain Control Module (PCM). I am seeking guidance on how to properly test or diagnose the PCM to confirm whether it is indeed the root cause. Any advice on diagnostic procedures or potential next steps would be greatly appreciated.