P0144 Fault on 2007 Mazda 6 2.3L: Valid Code or Misdiagnosis? O2 Sensor Circuit High Voltage (Bank 1, Sensor 3)

Hello everyone, I'm experiencing an intermittent P0144 diagnostic trouble code on my 2007 Mazda 6 2.3L: 'O2 Sensor Circuit High Voltage (Bank 1, Sensor 3)'. This is puzzling because the vehicle is equipped with only two oxygen sensors — one upstream and one downstream — not three as some sources suggest. The check engine light activates intermittently and then turns off after a few minutes. After checking the official service manual and reviewing multiple online forums, I've found that P0144 is not listed for this specific model year or trim. This raises concerns: Is this a misdiagnosis? Could it be a generic code triggered by an issue with the downstream O2 sensor despite the vehicle's design having only two sensors? I haven't performed any physical testing yet, as I need to wait for warmer weather to safely lift the car and inspect under the hood. I'm seeking input on whether this code could still point to a downstream O2 sensor fault or if it might be an incorrect reading due to software interpretation or emissions compliance settings. Any insights or suggestions would be greatly appreciated.