O2 readings

[Progas]

I finally got my HP tuner, and decided to do some scanning before I do anything. Well I scanned my car all the way to work (about 70mi), and then reran the saved scan. I noticed my O2 sensor is all over the place. It oscillates like a sine wave. It goes from about 63mV to 850mV back and forth really fast. Is this normal? I thought the O2 would read relatively steady dependant upon throttle.

I dont have a check engine light on either. I have not scanned for codes yet not sure I will find anything if I do.

 

[Scimmia]

Yes, this is totally normal for cruising at part throttle. The computer adjusts until you go lean, then adjusts it until you go rich, so it keeps going back and forth.

 

[TDCRacing]

Yeah it's normal. The only time the o2's will lock in is when you go into PE. Wich is at about 35% TPS on a stock PE vs. TPS table.

 

[Progas]

Thanks for the replies

I guess I just always assumed the computer would compensate faster than that, and hold a more steady reading. I will check the log when it was in PE mode, and see what it showed. I thought maybe the sensor was bad.

 

[TDCRacing]

When the sensor is bad or even a wire has melted on the exhaust or has been cut they usually read a fairly steady reading all the time. Then you will get an slow switching code or something like that

 

[Sabrewings]

I guess I just always assumed the computer would compensate faster than that, and hold a more steady reading.

It's not that it can't compensate fast enough. That's how it tests the sensor's operation, by swinging it back and forth to make sure it responds appropriately.