po155 02 heater circuit bank code

hi there i have 2002 bmw 325i with the engine light on i when to autozone the codes are po155 02 heater circuit bank 2 sensor 1 and po135 02 heater circuit bank 1 sensor 1 they told me i need replace only one sensor is that true? and were is locate this sensor? thanks in advance

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW 3 Series (E36) Oxygen Sensor Replacement

[Wayne 962]

Seems odd that both those codes would come up. The heater circuit on the oxygen sensors is used to heat them up when the car is cold so that you can get accurate readings right away. In all reality, this only affects the performance of the car when it's stone cold, and only for a few minutes too at startup. The codes seem to indicate problems with two sensors, which is unusual. I would reset the codes and see if they come back - having a broken heater circuit in the oxygen sensors is not going to affect the performance of your car very much at all.

- Wayne