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Old 05-18-2014, 09:58 AM   #1
Yangs
 
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Up stream o2 Oxygen sensor above 3 volts?

I test and replace o2 sensor before on other cars but this time with my Yaris I have a very bizarre situation. While the car is fully warm in operation temperature According to my multimeter, it show's little above 3.00 volts and it doesn't fluctuate from 0 volt to 3.00..."a steady voltage" I try to give it some gas but it still doesn't fluctuate. What's very strange is that the instrument cluster does NOT throw any trouble code and even thou I stick in a diagnostic scan tool it doesn't show any trouble code and emission status are good. Not to mention MY GAS MILEAGE WENT GARBAGE!!! I never heard 3 volts before on a o2 sensor. Maybe Toyota did some thing different from other car manufactures or maybe I have a bad o2 or a short some where?

Also the down stream o2 sensor read 0 volts at idle.
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Old 05-18-2014, 10:42 AM   #2
CTScott
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Quote:
Originally Posted by Yangs View Post
I test and replace o2 sensor before on other cars but this time with my Yaris I have a very bizarre situation. While the car is fully warm in operation temperature According to my multimeter, it show's little above 3.00 volts and it doesn't fluctuate from 0 volt to 3.00..."a steady voltage" I try to give it some gas but it still doesn't fluctuate. What's very strange is that the instrument cluster does NOT throw any trouble code and even thou I stick in a diagnostic scan tool it doesn't show any trouble code and emission status are good. Not to mention MY GAS MILEAGE WENT GARBAGE!!! I never heard 3 volts before on a o2 sensor. Maybe Toyota did some thing different from other car manufactures or maybe I have a bad o2 or a short some where?

Also the down stream o2 sensor read 0 volts at idle.
With the sensors used on the Yaris the voltage is kept constant and the ECM measures the current required to maintain the voltage, so you can not use a volt meter to troubleshoot them other than seeing if they are completely dead.
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Old 05-18-2014, 01:37 PM   #3
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Originally Posted by CTScott View Post
With the sensors used on the Yaris the voltage is kept constant and the ECM measures the current required to maintain the voltage, so you can not use a volt meter to troubleshoot them other than seeing if they are completely dead.
thanks for the info!!!
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Old 05-19-2014, 09:33 PM   #4
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Originally Posted by CTScott View Post
With the sensors used on the Yaris the voltage is kept constant and the ECM measures the current required to maintain the voltage, so you can not use a volt meter to troubleshoot them other than seeing if they are completely dead.
i notice its not a o2 narrowband sensor. its actually an air/fuel wideband sensor. im surprise.
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Old 05-19-2014, 09:47 PM   #5
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i notice its not a o2 narrowband sensor. its actually an air/fuel wideband sensor. im surprise.
Correct. The downstream one is a normal 02 sensor, but it too is operated in a current control mode.
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Old 05-19-2014, 09:53 PM   #6
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Correct. The downstream one is a normal 02 sensor, but it too is operated in a current control mode.
im really dumbfounded about it. i though i was going nuts. i got my yaris 2 years ago. im new to the toyota world.
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Old 12-16-2017, 03:39 AM   #7
ojeysky
 
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Quote:
Originally Posted by Yangs View Post
I test and replace o2 sensor before on other cars but this time with my Yaris I have a very bizarre situation. While the car is fully warm in operation temperature According to my multimeter, it show's little above 3.00 volts and it doesn't fluctuate from 0 volt to 3.00..."a steady voltage" I try to give it some gas but it still doesn't fluctuate. What's very strange is that the instrument cluster does NOT throw any trouble code and even thou I stick in a diagnostic scan tool it doesn't show any trouble code and emission status are good. Not to mention MY GAS MILEAGE WENT GARBAGE!!! I never heard 3 volts before on a o2 sensor. Maybe Toyota did some thing different from other car manufactures or maybe I have a bad o2 or a short some where?

Also the down stream o2 sensor read 0 volts at idle.
Am seeing this same reading on my scanner. The upstream sensor reads between 3 and 3.3 while downstream reads between 0 and 0.9. From what I read here it seem it's a normal behavior? as I had thought both were supposed to read between 0 and 0.9 so I was quite concerned as well.

Thanks
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