2004 Cadillac SRX Now Has No Power or Idle Issues with Persistent P2119 Code

I purchased a used 2004 Cadillac SRX that previously ran smoothly. However, recently it began exhibiting severe power loss and fails to maintain idle—only starting with a very rough idle. I've already replaced both the throttle body and electronic accelerator pedal. The only recurring diagnostic code is P2119. I've checked all engine ground connections and relevant fuses, but there's no 5V signal detected at the throttle body sensors. Does anyone know if a 5V reference voltage is required at these sensors? If so, where does this power originate? My code reader shows accurate readings, but I'm not very familiar with the underlying electrical system.