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Where is the rear O2 sensor located?

(2002 Hyundai XG350)
in Polk City, FL on February 13, 2011
Got a P0141 OBDII code, which the site says is a "rear oxygen sensor heater circuit malfunction". Where exactly is this sensor located? If it's reasonably accessible, I'll replace it this afternoon, otherwise I'll have to camp out on the dealer's doorstep tomorrow morning.
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Popular Answer
Oxygen sensors are identified by bank and sensor position. Sensor 1 is always pre catalytic converter, sensor two is always post catalytic converter. If an engine is a 4 or 6 cylinder engine the whole engine is considered bank 1, if an engine is a V6, V8, V10....., the engine bank containing cylinder number 1 (first cylinder in the firing order) is considered Bank 1, the other bank is considered Bank 2. Interpretation Oxygen sensor designation B2S1 refers to Bank 2 Sensor 1, it will be the sensor on the engine side of the catalytic converter in bank two. Check this link to determine the cylinder that contains cylinder number 1.
on February 13, 2011
Thanks; that was helpful. I eventually found, buried on the Hyundai site, that Bank 1 is also called the "right" side of the engine ( I guess because if the engine were installed "normally", Bank 1 would be on the right side of the engine, viewed from behind), and also called the "rear" side, because as mounted (transversely) it's on the rear side of the engine. The O2 sensors are also referred to as "upper" and "lower", with the upper closer to the cylinders, and the lowers on the downstream side of the catalytic converters. So my sensor is both B1S2 and Rear Lower. It was easy to find after a quick crawl under the car, installed on the top side of the exhaust pipe, easy to reach with a short open-end wrench or a crowsfoot. In fact, the "special" Lisle socket for removing O2 sensors would be of no use in this situation.
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