O2 Sensor Heater Circuit -- Low Voltage at the Plug to the Sensor

[James Hapka]

The plug that leads out of the ECU (To the upper bank 02 sensor is delivering 9 volts of power). When I keep the multimeter positive probe on the plug hot wire and place the negative multimeter probe on the engine block I get 12.5 volts; Which leads me to believe that there is a grounding issue inthe 02 sensor wire harnass (In the car) itself. 2009 Corrolla LE 1.8L. Thus the new 02 sensor will not operate properly and I get code P0031. There has to be an easy fix for this but I cant figure it out... Other code I see is C1241. Please Advise.

 

[James Hapka]

I am thinking another test I could do on that plug is continuity and various tests on the New O2 sensor (I could have baught one that doesn't work - and "Assumed" that it was good); which would not make me very happy.

 

[Vincent Garcia]

Check chassis ground you are getting 12 volts of the negative terminal of the battery. 9 volts at sensor indicates a bad or lose or missing ground

 

[James Hapka]

Thanks Vincent.

What I found out (Over the weekend) is that the New O2 Sensor's Heater Circuit had no continuity and no resistance. In other words, it was defective (The Sensor was the cheapest I could find, and I now see why!). My problem was that I assumed that it was good (Being brand new and all). It is sort of embarrasing that I made that assumption as I spent significant time trying to figure out other causes.... Needless to say, I replaced the above stated O2 sensor with, yet, another (Denso) and the car now runs flawlessly.

I had to pay $70.00 for the Denso Model, but it was well worth it.

I really appreciated your response, however.

Good day, Sir!