Hi, I have an S500 with 120,000 miles on it . The check engine light came on and my code reader listed 0136 and 0141. I think these might be O2 sensors. If someone could confirm this and tell me where they are located, I would greatly appreciate it. Thanks, Adam.

 

Both Bank 1 Sensor 2 codes so technically only the rearmost sensor on the RHS (from inside looking forward) is giving a problem.

Sure the connector plug is correctly seated?

The rear sensors are in the exhaust pipe roughly level with the gearbox. The electrical connecto is usually bolted to the gearbox / engine joining face at the very bottom of the transmission.
The forward sensors are in the exhaust downpipe and the wiring runs from the firewall.

Will need to remove undershieding to gain access / visibility of the sensors. Simple job. Just a few obvious screws.

Hope this helps.

At 120k it might be prudent to change more than one sensor. 4 in all.

To actually check that the sensors are good / bad you need to have the car hooked up to a diagnostic (real time) computer and observe the sensor waveform.

 

thank you for the information , I was able to locate and replace the rear O2 sensor with little difficulty. As for replacing all 4 sensors, at $225 each I think I will wait until they fail to replace them. The code disappeared immediately and has not returned. I appreciate your assistance. Regards, Adam.

 

I'm pleased my advice was helpful.

I wonder what caused just one sensor to go down. Still think a bad connection may have been the issue which was "corrected" when the sensor was changed.
O2 sensors usually go down due to contamination but by definition this knocks out the front sensors (and usually both banks) first.

Anyway all is now OK.

Stuart.