Q: P0139 HO2S-12 (Bank 1 Sensor 2) Circuit Slow Response - 2005 Honda Accord

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My car (Honda Accord EX Coupe L4 2005) had this code (P0139 HO2S-12 (Bank 1 Sensor 2) Circuit slow response) 2 month ago. But i didn't see any symptom; so i erased the code because i thought that should have been the sensor getting old. This morning the same code came up. My question is What is most probable in this case a bad sensor or a leaking in the fuel injector system?

My car has 101000 miles.
My car has an automatic transmission.

This code indicates that the rear oxygen sensor is not properly reading the oxygen content and adjusting the air/fuel ratio as it is supposed to. This can be caused the by the sensor not working properly, the wiring to the sensor being damaged or broken or potentially an exhaust leak. I would recommend checking the following to correct this:

  • Check and fix any exhaust leaks
  • Check for wiring problems (shorted, frayed wires)
  • Check the frequency and amplitude of the oxygen sensor (advanced)
  • Check for a deteriorating/contaminated oxygen sensor, replace if necessary
  • Check for inlet air leaks
  • Check the MAF sensor for proper operation

If you need some help with this, you may want to consider having an expert from YourMechanic come to your location to properly diagnose the trouble code and correct this problem.

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