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O2 sensor voltage values

aldive

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1999 XLT
The is a question for Robert, since he seems to be the most knowledgable on such mattters, however, anyone else please chime in....

What are the voltage values suposed to be on the O2 sensors during an OBD II scan?
 



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My manual says 6 ohms
 






I am interested in the operating voltage ( and changes ).
 






With the HO2S connected and the engine running, measure the voltage with a DVOM between terminals HO2S and SIG RTN (GND) of the oxygen sensor connector. If the voltage readings are swinging rapidly between 0.001-1.1 volts, the sensor is probably okay.

Hows that?
 






Thanks.... I was monitoring with an OBD II scanner.

Robert, please chime in.....
 






The operating limits of the O2 sensors is 0.1VDC - 0.9VDC. The upstream sensors should alternate above an below 450mV at least every three seconds. The downstream ones should be slower, but my CD doesn't say how much. The value should never be negative. The upstream sensors will switch as soon as the engine is running but the results may not be accurate until after going into closed loop. The downstream sensor will only switch after going into closed loop.

One of the O2 sensor tests is response. The PCM measures the ratio between the upstream O2 sensor and the downstream sensor. If the ratio gets too close to 1:1 it trips a catalyst efficiency error code on the bank that it detects the error. In other words if the downstream sensor is switching as quickly as the upstream sensor the catalytic converter isn't doing its job. At the other end of the spectrum, if the upstream sensor doesn't swith at least every three seconds, your PCM will adjust the fuel trims accordingly. If your long term fuel trims get adjusted to their maximum allowable value (+/- 20%) your PCM will either throw a long term fuel trim error or a slow response on the applicable O2 sensor.
 






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