Error code: P0137 O2 Circuit Low Voltage (Bank 1 Sensor 2)

2012 TOYOTA RAV4
79,000 MILES • V6 • 2WD • AUTOMATIC
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MLEEPER
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  • 1 POST
I'm having a heck of a time finding out if this is upstream or downstream, and where I've had several parts stores give me opposite information. Please help. :-) Thank you.
Apr 11, 2019 at 2:13 PM
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SCGRANTURISMO
  • ✓ASE Certified Mechanic
  • 4,897 POSTS
  • ASE Certified Mechanic
Hello,

This is the downstream O2 sensor. This is how you tell upstream from downstream. The O2 sensor that is closest to the engine is the upstream sensor. Then there will be the catalytic converter going down your vehicle's exhaust from the engine to the tailpipe. The catalytic converter is, I repeat for emphasis, is the "stream" in upstream and downstream, and then the downstream O2 sensor. So closest to engine upstream, farthest from the engine and after the catalytic converter, downstream.

Thanks,
Alex
2CarPros
Apr 11, 2019 at 8:00 PM
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