2003 Saturn L300 P0001 Code: Fuel Volume Regulator Circuit Open - O2 Sensor Issues and Engine Stalling

I was driving my 2003 Saturn L300 home when the car suddenly lost power. I had to keep pressing the gas pedal to maintain speed, but it eventually stalled and I needed a tow truck. After letting the vehicle sit for several months, I recently completed a smog check in California. During that inspection, I was advised to replace the O2 sensor on Bank 2, Sensor 1. The technician noted that Bank 1's Sensor 1 was nearing failure and that both downstream oxygen sensors were showing weak readings. I purchased a Centech OBD2 code reader, which now displays a P0001 fault code: 'Fuel Volume Regulator Circuit Open'. I recently replaced the upstream O2 sensor on Bank 1. However, despite this repair, the vehicle still runs poorly. When I try to accelerate, it stutters and dies immediately. I only manage to keep it running for about 30 seconds before it shuts off. I now let the car idle briefly when starting—just enough to run for a minute or so—and then it stalls again. As an older-school mechanic, I'm skeptical of modern diagnostic tools and some of the recommendations I've heard from professionals who claim you need a Harvard degree to fix cars. I believe these systems are overcomplicated. I'm seeking advice on how to properly diagnose and resolve this P0001 code in my 2003 Saturn L300. Any insights or troubleshooting steps would be greatly appreciated.