Mazda Repair: Mazda 6 repair, engine sensors, o2 sensors

Question
Have a Mazda 6 2205 V6 station wagon. Have four engine trouble codes. Two say "O2 sensor stuck lean Bank 1 sensor 1 and Bank 2 sensor 1" and two codes that say "system too lean, off idle speed Bank 1 and Bank 2". Codes P2177,P2197, P2195, and P2179.
Could two O2 sensors both be bad and causing these codes and engine light? If so where are they located on engine I guess to replace. Someone told me he thought there were four sensors on this engins?
Thanks

Answer
before replacing sensors check other problems that could cause you to be running lean or rich sensors are exspensive and hardly ever the fault. could be as simple as a vacccum leak or a problem with the fuel deliver system or ignition system. even a dirty air filter can set an O2 sensor fault, fault Pcv valve, egr valve, timing being off, or the engine not advancing or retarting timing at the correct time. diagnosing O2 sensor faults isn't something i wouldn't  suggest the home mechanic to do. there is alot or probabilities not just the sensors not working properly and if both are showing a fault i'd say it's not the sensors and it's other engine sensors or components that effect the reading of the O2 sensor