1999 Toyota Camry P0125 Code: Thermostat vs O2 Sensor Diagnosis - Closed Loop Control Issues

I own a 1999 Toyota Camry with a 2.2L engine and AC (CE model, automatic transmission). After purchasing OBDWIZ software to clear diagnostic codes, I attempted a smog test but failed severely—rated as a 'gross polluter' due to high emissions. Emissions readings: - HC PPM: 123 (maximum allowed: 55) - CO%: 3.92 (maximum allowed: 0.5% After the check engine light reactivated, I retrieved codes: P0125, P1135, and P1133. I initially believed P0125 (Insufficient Coolant Temperature to Enter Closed Loop Control) was the primary issue, so I replaced the thermostat. However, after multiple cycles of clearing codes and retesting, I still see combinations of P0125, P1135, and P1133—these do not always appear together. I logged the coolant temperature: it reached approximately 194°F at 3.65 minutes after engine start, with the CEL triggering around 3.5 minutes. At that point, codes P0125 and P1133 were present. My question is: What is the official minimum coolant temperature required to enter closed loop control? And within what time frame must this temperature be reached? I've read in other discussions that Toyota may misapply the P0125 code—using it not for actual coolant temperature issues, but as a symptom of an oxygen sensor (O2) failure. Codes like P1135 and P1133 could support this theory. So, is my issue likely due to a faulty thermostat, a failing O2 sensor, or both? What additional diagnostic steps can I take to accurately isolate the root cause? Thanks for any insights or testing suggestions!