not long ago I posted a question about a suspicious datalog reading of my Bank1 O2 sensor. I replaced it with a new Bosch, and recently had the chance to re-log to see if anything changed. Doesn't look like it:



Original Log - O2's in Black (Bank2), Red (Bank1). Bank 1 looks like it is going squirrley - very erratic.




Latest Logging - same colors. Bank 1, in Red still looks erratic compared to Bank 2:




For those of you who have done logging, or are familiar w/ O2 sensors, does this look right? Should they both be showing similar behaviour, or is it to be expected that either one could be going crazy like that?

Also, there is no CEL, and no codes, so I don't believe either the old or new O2 is faulty.

If this reading is showing a problem, what might it be?

In my reading here and some discussion w/ TP, it seems like this might be a cause of my poor MPG (like 15 highway for a 4.6l w/ AF1 and Xcal2 tunes).

Any suggestions would be appreciated.

 

YOur back 1 sensor actually looks pretty normal for those load conditions.

I'd be more concerned about why your bank 2 sensor isn't switching at a frequent basis.

I'd suggest reinstalling the original sensor back into bank 1 and installing your new sensor into bank 2 then retest.

Under idle or steady-state conditions, both banks should be switching relatively rapidly, every 2-4 seconds.

I'd also like to see what your short and long term fuel trims look like.

Steve

 

that the erratic behaviour is what should be expected? Should they both be like that? (sorry for the noob questions; I just don't know).

Perhaps I swapped the wrong O2?

 

Both banks are in synch with one another, almost exactly. I can post a pic of that too if it would help.

 

See 4th line in above post. Your graph does not show bank 2 to be switching except in very gross terms instead of the expected every several seconds. Bnak 1 is not "erratic", it is normal. The lack of bank 2 switching as per your graph is what is not normal.

Bank 2 is the driver's side, bank 1 is the pax side.

Steve

 

Thank you Steve. That understanding is what I DIDN'T have when I put the new Bosch in. Since your post I've been reading up on what O2's do in terms of how they take reading and you are spot on.

Your post has sort of explained a lot to me about the feedback between O2's, Open loop etc.

I am sort of surprized that there is no CEL or codes? I guess the sensor is functioning by giving feedback, but just not the right kind.

Do you think the way bank 2 is functioning would have an effect on MPG's?

Thanks for taking the time to look at my data.

 

Hey Steve, do you use propane at a idle to drive the 02s and test the voltage when they switch?