2000 Ford F250 7.3 PowerStroke: Multiple DTC Codes P1605, P1641, P1662 and Poor Acceleration

I'm having trouble with my brother's 2000 Ford F250 7.3L PowerStroke truck. The vehicle is exhibiting severe performance issues — almost no acceleration, very slow response even when the throttle is fully depressed, and occasionally produces full white smoke from the exhaust. Multiple diagnostic trouble codes (DTCs) have been pulled: P1605 (PCM Keep-Alive Memory Error), P1641 (Fuel Pump Primary Circuit Failure), P1662 (EDM_EN Circuit Failure), and P1690 (Wastegate Control Solenoid Circuit Malfunction). All codes appeared simultaneously, suggesting a shared underlying issue. While the symptoms point to potential wiring or connector problems, I'm unsure whether there's one common circuit or component affecting all these systems. The fact that multiple circuits are failing at once raises concerns about a single fault location — possibly a damaged harness, corroded connector, or power supply issue. Any insight into what could be causing this common failure across these codes would be greatly appreciated. I'm currently at a loss on where to begin troubleshooting and need help identifying the root cause.