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6.7 Cummins setting 02 sensor faults
Posted to Technical Tips Forum on 1/11/2017 11 Replies

Just went through a battle on a Ram diesel setting multiple fault codes as follows:

P014D 1/1 02 sensor slow response lean-rich P013b 1/2 02 sensor slow response lean-rich P0471 Exhaust pressure sensor performance P1451 DPF system performance P2463 DPF soot accumulation P242F DPF filter restriction ash accumulation P2bac NOX exceedance deactivation of egr

To start out with these are usually fairly cut and dry. We may or may not have a soot issue. If a over fueling condition is found it needs to be identified and corrected. Next I will typically begin by performing tsb 25-003-13 (if it has not yet been performed) which involved replacing 02 (1/1 and 1/2 sensors) harness with a overlay. Also making sure the 02 sensor module feed and bus circuits are gold plated terminals (overlay comes with gold pins for all terminals). If they are found to be tin then install gold terminals. Next is to remove 02 sensors and blow soot out with compressed air. Cleared faults, Regen if needed and test drive. Perform zero fueling events on road test by going wide open throttle and then immediate deceleration coast down. If MIL comes back on replace 02 sensors. If the DPF soot load is too high generally driving them on the highway for 50 miles will allow the PCM to perform a active Regen and will return to a normal soot load. If not DPF gets replaced. So like I said before not too big of a deal.

In the case of this particular truck the engine ran great and everything tested out in relation to the 02 sensors and after treatment system. What enviably repaired this vehicle was replacing the Mass air flow sensor. The only way I was able to spot this was from doing a data recording on this and another know good truck and comparing. Found that at a stable idle the MAF was under reporting by 3-5 G/S. Also the Baro was slightly elevated (28.6 on customer truck and 28.1 on donor truck). I will say that using the Modis in OBD global mode as apposed to Witech was the best way to view this.

Surprisingly the MAF was the root cause of every fault code listed above. In the case of a Cummins wide band 02 sensor, and information found flow charts, chrysler dca books, and service information indicate that the MAF does not have any bearing upon the PCM's ability properly verify 02 sensor operation. Obviously this is incorrect. 02 sensors on Cummins 6.7 are not used for fuel mixture purposes as a diesel does not trim fuel like a gas engine. According to SI the primary purpose is to control/verify EGR. I do think that they also have a hand in the regeneration process as well. Evidently the pcm is using intake airflow to judge if the 02 sensor current is near enough to what is expecting to see. In this case I think the PCM just was not capable of blaming the MAF so it blamed the 02 sensors. There was no information to suspect the MAF in Star online, identifix or IATN so hopefully someone can benefit from this in the future.

Skyler from Nebraska

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car Vehicle Data

2011 Ram 2500 Laramie 6.7L

Engine6.7 L
Trans6-speed Automatic (Electronic)