1998 Toyota Camry Air-fuel sensor

Check engine light is on. OBDII is telling me code P0125 ( Insuficient coolant temp. For closed loop fuel control) and when I select Toyota I get P1135 and P1133 codes ( Air-Fuel sensor heater circuit response mulfunction). I am trying to understand what could be wrong.I am a little confused with sensor locations. Which one is bank 1 and 2 sensor 1 or 2. I need to know how to test the sensors, and what else could cause the codes if the sensor itself is not bad. I heard about sensor contamination bt antifreeze or oil but I am not sure how it could happen and where I should look into. Thanks for inputs in advance.
Renate
P.S I had a bad thermostat that I replaced and the temp. Is normal now. I cleared code but keep coming back.