Hyundai Repair: 2000 elentra check engine light on, P0136, advanced auto parts, worst case scenario

Question
Couple of days ago I found the check engine light was always on (2000 Electra). I took it to advanced auto parts and they told me the error code was P0136 (O2 bank 1 sensor 2). What shall I do with it? Replace the O2 sensor? Or are there any other possibilities to cause the error?

Thank you very much! It is my first car. I am somehow worried about it.  

Answer
I've seen two problems with signficant frequency that can cause the P0136 code:
1.  Sensor wiring rubbed through on axle shaft.
2.  Problem with heater in oxygen sensor.

I'd recommend checking the wiring for the rear oxygen sensor.  The sensor is screwed into your front exhaust pipe, just behind the engine.  It should be clipped onto the support bracket that runs between the engine block and intake manifold.  If the wiring is damaged, repair it or replace the sensor (if on the wiring attached to the sensor).  If the wiring is okay, go ahead and replace the sensor as it's the probably cause.

The good news is that P0136 indicates a problem that will not affect the way your vehicle runs and presents no hazard to the vehicle.  The worst case scenario would be that one of the power wires rubs through on the axle and causes a fuse to blow, making your car stop running.  Your rear oxygen sensor's only purpose is to allow the engine control module (ECM) to assess the performance of your catalytic converter by comparing the readings of the rear oxygen sensor to the front oxygen sensor.  If the rear sensor isn't working properly, it simply means that the ECM doesn't know how well your converter is working.