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Old 02-21-2001, 11:43 AM   #1
Spectre23
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Join Date: Sep 1999
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Location: Murray, Ut, USA
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2013 STi
CBS

Question O2 Sensor Voltage

I know this has been covered but I did a search and couldn't find it.

I have an AFC with the input 2 on my O2 sensor. Unfortunately it is on my rear O2 sensor. What voltage do I want to see on that O2 sensor. Also, is higher voltage richer or leaner? Currently I am seeing about .65v and my exhaust smells like crap telling me it is rich. Is the front O2 sensor a wide band sensor on all RS's or just 2000 and newer?
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Old 02-21-2001, 11:48 AM   #2
RidinLow
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Only MY00 & up cars have the wideband sensors. .6x is way too rich... I think you should be seeing .8x, but don't quote me on that.
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Old 02-21-2001, 05:50 PM   #3
the spacecowboy
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afc....o2 sensors....the super afc is hooked to the o2 sensors?...what wires are these...
or the wires going to the ecu are o2 sensor wire...

sorry for the stupid Q

space
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Old 02-21-2001, 07:22 PM   #4
Spectre23
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I beleive they call it the "Blue Wire Mod". It is an optional connection you can make with the wire that would go to the second mass airflow sensor on a Supra. I don't know if it goes to the ECU or the wire itself, I didn't wire mine.
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Old 02-22-2001, 12:24 AM   #5
stimpy
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The wideband O2 sensor is only on MY00+. Anything before that has the standard narrow band O2 sensor with readings of 0-.9v. Higher is richer as I recall. I would recommend relocating your A/F readings to the front O2 sensor. Often the rear O2 sensor will read leaner than the front O2 sensor because of the cats.

-Jon
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Old 02-22-2001, 04:31 AM   #6
philrb
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At idle you should get fluctuating voltage from about .3 to .7 (the fluctuating aspect is more important than the actual voltages). When you open the throttle and hold it open to about 2k rpm the reading should go down for a moment and then up over .5 and then stabilize around .5.
The engine must be HOT as the O2 sensor does it's job at about 700 degrees F.
If you do take it out and it's cruddy looking you can salvage it by cleaning it off with a stainless steel brush. When installing DO NOT use silicone (dielectric)grease (the glop used for the other engine bay connectors). This'll add impedance and throw the voltages off.
If you still have problems run the car at legal speeds at 4500 rpm for a few minutes and then re-check your voltages. If you do buy a new sensor make sure it's Bosch.
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Old 02-22-2001, 06:21 AM   #7
Spectre23
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Is that .5v for the front or rear sensor? Sounds like maybe the rear.
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