2009 Chevy Traverse P0496 and P0221 Codes: Stabilitrak Turns Off During Idle - Possible ECM or Wiring Issues

After replacing the transmission, timing chain and sprockets, throttle body, and throttle position pedal sensor, my 2009 Chevy Traverse runs well under normal conditions. However, after idling for a few minutes, the Stabilitrak system unexpectedly shuts off. Two days ago, this occurred and triggered a pending code P0496. I replaced the purge valve as recommended, and the vehicle ran without issues for one full day. Today, while idling again, the car threw a new code: P0221, which points back to the throttle position pedal sensor. I've researched potential causes and believe this could be related to ECM malfunctions or faulty wiring connections. While I’ve read about oscilloscope testing being effective, I don’t have access to such equipment or diagnostic tools at home. I’m seeking advice on how to troubleshoot these persistent codes without specialized tools. Additionally, I'm concerned that the intermittent shutdown of Stabilitrak—especially during idle—is both a safety risk and an emission failure issue. This behavior seems particularly dangerous and frustrating given its impact on vehicle stability. Any insights or suggestions would be greatly appreciated.