[Scrippy]

Guys,

Anyone with BMWwhatsapp who can log their O2 sensors front and rear of banks 1 & 2 at engine idle can you post a screen shot? I want to compare to my numbers. I'm already weary about my two sensors behind the cats showing numbers off from each other yet the fronts are pretty much identical.

[Cloud9blue]

I wouldn't worry about it. Post cat O2 readings are rarely identical.

[Scrippy]

Originally Posted by Cloud9blue

I wouldn't worry about it. Post cat O2 readings are rarely identical.

Yeah but mine are constantly off by a almost a volt at times. Where as my sensors in front of the cats are always matching or within a tenth of a volt of each other. Also, at times my post cat sensors display 0 volts when logging. Usually 0 volts occurs when I let off for a stop.

[mweisdorfer]

Do you have a check engine light?

If not, I would not worry about it. The post cat only monitor the pre-cat's.

The pre-cats are what typically go bad after 100k-110k or so.

[Scrippy]

Originally Posted by mweisdorfer

Do you have a check engine light?

If not, I would not worry about it. The post cat only monitor the pre-cat's.

The pre-cats are what typically go bad after 100k-110k or so.

The errors have produced a check engine light. They all pointed to bank 1 post cat. I've cleared them and driven kinda hard in attempts to burn out crap. I just had a walnut blast, valve cover gasket, rear turbo charge pipe replacement, oil change, HPFP, all 6 injectors and the God damn cabin filter done at my local dealership. So to now see several codes popping up for the same sensor out of 4.......I'm pissed they didn't do or even recommend it. How do you drive 5 miles and get code after code after spending 6 grand? Hence my diligence asking folks before just replacing 2 at a time. I wanna know how everyone else's behave at idle. INPA/WHATSAPP/SSS and several more tell you. Plus....your wrong in what you said. The O2 sensors do factor in on Air/Fuel mix. So a bullshit result on the rears will make the DME compensate fuel trim. Most definitely this will produce a sluggish whip brah!

[Tzu]

Bad cat, exhaust leak or bad narrowband sensor. The DME constantly adjusts AFR at idle between 13 and 15 AFR for O2 sensor tests. I've never had the wideband O2s sitting perfectly at one voltage, and if yours are, I'm guessing your diagnosis app has a slow sample rate or is really smoothing the readings.

[Scrippy]

Originally Posted by Tzu

Bad cat, exhaust leak or bad narrowband sensor. The DME constantly adjusts AFR at idle between 13 and 15 AFR for O2 sensor tests. I've never had the wideband O2s sitting perfectly at one voltage, and if yours are, I'm guessing your diagnosis app has a slow sample rate or is really smoothing the readings.

You are correct in that the sample rate of the BMWwhatsapp is slow. You are also correct that banks 1&2 will never be perfectly matched. I wasn't saying they should be PERFECTLY matched but let's be real.....they should be 95% accurate to each other. It's a 6 cylinder motor not a 24 cylinder motor like in a prop plane.