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Thread: P2271 / P2BAC

  1. Top Of Page | #1
    Taistee's Avatar

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    P2271 / P2BAC

    I’m going to frontload this with a few questions:

    1. Can I continue to drive with the check engine light on for Bank 1 sensor 2 stuck rich without causing damage?
    2. What are normal readings for O2 sensors (for troubleshooting purposes)? Is it like a gasser, where you expect between .1 volt and .9 volts? (And my scanner gives me O2 sensor readings in mA instead of volts, which I don’t really understand either)

    I bought my 2012 Ram 2500 6.7L with 146,500 miles on it, everything stock. Found a stored P04DB (CCV filter) code, so I did the 67,500 maintenance on it and that went away. However, it recently threw a P2271 code, Bank1 sensor 2 O2 sensor stuck rich. I know on a gasser the pre-cat O2 sensor controls the air/fuel mixture, and the post cat measures the converter efficiency. So to drive a gasser with the pre-cat O2 sensor malfunctioning will cause incorrect air/fuel mixture.

    But do the O2 sensors on a Ram diesel also tell the ECM how to mix the air/fuel?

    Not too long after this O2 sensor code I also got P2BAC, “NOx exceedance- deactivation of EGR.” Which I think is an info-only code for a de-rated engine until emissions are fixed. But I haven’t noticed any difference in performance, and hey, I guess this means EGR has turned itself off? Kinda good maybe?

    Most importantly, can I drive like this without causing irreparable damage.

    I bought a Bosch O2 sensor but have not swapped it yet, pending the collective knowledge of the membership.


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    2012 2500 4WD, CCLB 68RFE, 2.75" Carli Level with Bilstein 5100s, and still a ways to go...

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  3. Top Of Page | #2
    P2609 Fanatic Electrojake's Avatar

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    Re: P2271 / P2BAC

    Greetings & welcome @Taistee! Great first post.

    Being a non-mechanic I too will be watching this thread for input from the crew here.

    I have a 2016 and the emission psychology on pre-2013 engines is significantly different than on a post-2013 truck so this should be a learning experience.

    NOTE: As a non-mechanic I'd guess that since the ECU obviously knows there is an O2 sensor malfunction, then it should also default to a non-destructive fueling map (open-loop per se).

    Following.

    2016 Longhorn 3500, 4x4 shortbed CrewCab, Cummins HO/AISIN, 99.8% stock.
    * Hauling a 2018 Northstar Arrow-U. Scale weight 12,400 Lb.

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  5. Top Of Page | #3
    DDP's Avatar

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    Re: P2271 / P2BAC

    Quote Originally Posted by Taistee View Post
    I’m going to frontload this with a few questions:

    1. Can I continue to drive with the check engine light on for Bank 1 sensor 2 stuck rich without causing damage?
    2. What are normal readings for O2 sensors (for troubleshooting purposes)? Is it like a gasser, where you expect between .1 volt and .9 volts? (And my scanner gives me O2 sensor readings in mA instead of volts, which I don’t really understand either)

    I bought my 2012 Ram 2500 6.7L with 146,500 miles on it, everything stock. Found a stored P04DB (CCV filter) code, so I did the 67,500 maintenance on it and that went away. However, it recently threw a P2271 code, Bank1 sensor 2 O2 sensor stuck rich. I know on a gasser the pre-cat O2 sensor controls the air/fuel mixture, and the post cat measures the converter efficiency. So to drive a gasser with the pre-cat O2 sensor malfunctioning will cause incorrect air/fuel mixture.

    But do the O2 sensors on a Ram diesel also tell the ECM how to mix the air/fuel?

    Not too long after this O2 sensor code I also got P2BAC, “NOx exceedance- deactivation of EGR.” Which I think is an info-only code for a de-rated engine until emissions are fixed. But I haven’t noticed any difference in performance, and hey, I guess this means EGR has turned itself off? Kinda good maybe?

    Most importantly, can I drive like this without causing irreparable damage.

    I bought a Bosch O2 sensor but have not swapped it yet, pending the collective knowledge of the membership.


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    It could be a couple things.

    Change that sensor and see what happens.

    You will most likely find it extremely dirty and needing replacement.

    Some customers have stated that they or the dealer found a wire harness that needed to be replaced with these same codes.

    I would get it taken care of as soon as ya could.

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    Taistee's Avatar

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    Re: P2271 / P2BAC

    Thanks for the replies, guys!

    I had previously taken the sensor out, cleaned it, and put it back in. It wasn’t too bad when I pulled it. The money light came on again though, which is when I reached out here.

    I replaced the part today, and it was a Denso sensor, not Bosch. As I understand it Bosch sensors don’t play nice with our Rams.

    I don’t drive it as much as I’d like, so it might be a while before I report back with results.

    Also, I am aware of the TSB for this issue, and it looks like the module/harness overlay has already been performed. Hopefully the sensor will do it! If not, well...I just might have to consider my options


    Sent from my iPhone using Tapatalk

    2012 2500 4WD, CCLB 68RFE, 2.75" Carli Level with Bilstein 5100s, and still a ways to go...

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  9. Top Of Page | #5
    SwingBeefRacing's Avatar

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    Re: P2271 / P2BAC

    Start with measuring the resistance between ground and the O2 sensor.

    If it’s above 10k ohms the sensor is okay if it’s below 10k ohms replace the sensor.

    I Hope this helps.


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  11. Top Of Page | #6
    Taistee's Avatar

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    Re: P2271 / P2BAC

    OK, so I replaced the sensor and have been driving it for a couple weeks, and the check engine light is gone!

    In this case I’m grateful for an uneventful outcome.

    Nothing worse than swapping out parts and still having problems.


    Sent from my iPhone using Tapatalk

    2012 2500 4WD, CCLB 68RFE, 2.75" Carli Level with Bilstein 5100s, and still a ways to go...

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