Hyundai Repair: 2006 Elantra - Check engine code: P0038, oxygen sensors, o2 sensors

Question
If this is correct and its a bad O2 sensor, how many O2 sensors are there on this model, where are they located, and how easy are they to change?

Answer
P0038 indicates a heater circuit malfunction for the downstream oxygen sensor.  This code can set if the sensor is unplugged, the wiring is damaged, or the sensor itself is faulty.  In the vast majority of the cases I've witnessed, the problem has been in the sensor or has been obvious if the wiring in the vicinity of the sensor is visually examined.

Your vehicle has two oxygen sensors, one upstream in the top of the exhaust manifold, and one downstream in the front exhaust pipe just to the rear of the flex area of the pipe.  The sensors are simple to replace by unscrewing from the exhaust.  For the downstream one which you'll likely need to replace, you should be able to simply unscrew it with a 22mm wrench.