Toyota Repair: 1998 Camry Error Code, air fuel ratio, otc scanner

Question
Ted, I have a 98 Camry, V6, automatic with 21,000 miles. My check engine light is on. I connected my OTC scanner and pulled code P0125. From what I have researched, it appears the thermostat may not be the issue but the O2 sensor. Is there any additional test I can perform to narrow this down before I decide which to go after?

Thanks for the advice.

Answer
The PO125 code indicates there is not enough coolant temperature for closed loop operation, one of the air/fuel ratio sensors located in the exhaust manifold, one on each bank, or maybe both may be the problem, there should be another code that tells you which one it is, if not the a/f ratio sensor voltages need to be checked using the scantool to see which one is deviating from the correct voltage, both should read very close to 3.29 volts with the engine warmed up at mormal operating temperature and at 2000 rpm.