Air to Fuel Sensor live scan voltage confusion

The live scan voltage for the A/F sensor (bank 1 sensor 1) is constantly around 3v, give or take, whether idling or driving.
I just saw this in the '01 FSM - new sensor time? or at the very least a concern?

I had posted some live scan data on here & no one said anything so I figured it was ok. Plus when I looked up voltage for the wideband, it stated 0-5v. I took this to mean live scan. It may have meant if checking the sensor itself?

 

I believe the earlier 1st gens had either an O2 sensor or AFR sensor upstream depending whether or not they were Califonia emissions.

Typical standard O2 sensor voltage is 0-1v (0.5v being 14.7:1 AFR, lower voltages being leaner and higher voltages being richer), an AFR sensor operates differently and scan data values for them vary but Toyota typically displays a voltage value for them (I believe around 3.3V is 14.7:1 AFR, higher voltages being leaner and lower voltages being richer).

 

Ok. Thank you.
so in theory, if I were to hit the throttle, say 2500 (rich), closed loop, the voltage should drop. i think there are other instructions in the FSM that use the 3.3. standard. Why the switch back & forth is what confused me. This is also specifically an ‘01 FSM.
Mine is a wide band afrs.

 

Guess that was kind of stating the obvious (the voltage drop), or rather, repeating what you stated. Just more talkin out loud.
Thank you….

 

& the talkin out loud helped because I realized the connection between using the fuel trim info to see if the afrs is working correctly. I mean the fact that the afrs may or may not drop is not enough to deem it defective. Fuel trims should be though…. I think….

 

Yea when you look at the ECM pinouts for a 2001 3.4 in service info it shows a standard O2 sensor for Federal emissions trucks and an AFR sensor for California emissions trucks.

Yea AFR sensors actually operate off current rather than voltage but Toyota displays it as a voltage that is a calculated value.

Yea if your fuel trims are good (+/- 10% total trim), there are no codes, and the truck is running fine then most likely there's nothing wrong with your AFR sensor.

 

The truck is not running fine. I've been chasing a high idle for what?, over a year? Yup. Over a year. I've checked a bunch of stuff, replaced hoses, gaskets, etc. Latest is I'm hearing hissing from the IAC air assist hose, which is new. However I also got a weird hum? buzz? noise off the IAC when I had the stethoscope near it. Not even touching it. So, that's tomorrow....

 

Most high idle conditions I see are caused by vacuum leaks, a failed IAC, or a mis-adjusted throttle body but there can be other causes such as an input to the PCM or a faulty PCM.
Vacuum leaks large enough to cause a high idle will typically cause a lean condition on a mass airflow engine and it sounds like you have pursued that avenue so I doubt that is your issue.

How high is your idle at operating temp?
One thing I have seen at least on a 2nd gen was a failed power steering pressure switch causing a high idle for someone, you could try unplugging that and seeing if it goes back to normal.

 

I actually had to replace the electrical connector to the switch. No idle change, however it did improve the PS whine.
I replaced the fuel pressure regulator & had a re-do on intake manifold gaskets & had a crappy fuel injector. That seemed to clear up the fuel trims. My spark plugs showed rich on 1,3,5 & lean on 2,4,6.
I checked the TPS numbers through the ECM & they check out, however the live scan numbers are confusing me. I flipped the throttle to 2800rpm & the tps went from 9.8 to 10.2. MAF bumped from 5-ish to 6-ish. Another flip to around 3500 & TPS went to 13-ish & Maf to 11-ish. Course other things changed as well, it's just you look at what jumps out. I suppose it could be really what's not jumping out that could be a culprit.

 

Sorry. Idle at op temp is around 1,000.