Q: My engine light turns on, and i went to autozone to diagnosis, and it's faulty o2 sensor. Would you be able to replace it?

If code P0136 sets the only way you can determine if the oxygen sensor has failed is to use an automotive scope to graphically depict the sensor output waveform (it will look roughly like a sine wave) and switching rate (around 5 hertz). Even if Autozone used a real time scanner (as opposed to just a simple code scanner which is probably what was used in your circumstance; by the way, if you car was NOT running during the "scan" they did NOT use a real time scanner) even a real time scanner only has the capability to show voltages. It can give a crude indication but to tell if the sensor is really bad you need a Mechanic with a scope. The fact of the matter is code P0136 has MULTIPLE and distinct possible causes including faults in the wiring to and from the oxygen sensor, exhaust leaks and defects in the catalytic converter. In fact, you can install a brand new oxygen sensor on your car, disconnect the wire to the sensor to simulate a "bad connection" and code P0136 will set! The point is the sensor ITSELF has to be tested. Now, it is possible that AutoZone has "guessed" right but once you act on guesses, as opposed to actual diagnostics and appropriate testing, you’re on the old "slippery slope". Better to ask for repairs according to the instructions, test just as the instructions require, and if bad, replace. If you want the sensor tested by a certified mechanic, and replaced if it is defective, please request oxygen sensor diagnostic/replacement and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.