After my Radix install and new tune, these two codes started to pop up. However, my wide band O2 sensor indicates everything is normal, no lean condition anywhere. I have removed the cats, but the tune took care of that. I read somewhere that because of back pressure the O2 sensors might not be reading correctly. The codes appear at easy driving. I erase the codes and drive normally and they will appear only after I turn off the truck and start it again. If I erase the codes, I can drive the truck for as long as the gas lasts and the codes will not appear at all, only when I turn off the engine, and start it again (no matter how long it stays off). I checked for vacuum leaks, exhaust leaks, O2 sensor wiring, and everything is normal. Any ideas? the truck drives very normal at all times. Oh, the truck is a 2008 NNBS 5.3 with Radix mp112, and has only 4000 miles on it.

I appreciate any help ...

 

The processing enablers for those codes are likely B: 2 Trips, Emissions Related. That is why they stay off until you start it again.

When you removed the cats did you weld or clamp in the new pipe? I would suspect an exhaust leak. If you are sure that you don't have an exhaust leak then check the Radix vacuum line plumbing. If all is good then it might be the intake gaskets under the Radix. You may have to lift and re-seat the head unit and intake manifold.

 

Hmmm, the pipes are welded. I am wondering though, of there is a true lean condition, it should show on my wideband, right? well, at normal driving conditions, the AFR is 14.5 - 14.7 and under boost is at 11.2 - 11.4 . This tells me it could be something else...

 

Are you still running a MAF ? Maybe it is possible the O2s are keeping your AFR in line but sensing a lean condition while doing it.
Can you log your STFT and LTFT and see what you get or monitor your O2s to see how they are switching and the range they are covering?
With your MAF still in place and trims active it is possible the AFR looks fine to the WO2 and the PCM is covering the lean condition up.
Not saying that it is not something else.....just not sure what it could be.

 

Yes, I can log short term and long term fuel trims using my hand held. What values should be right? I am still running my MAF, and you may be right, the PCM may be covering the lean conditions and the wide band is seing correct values. Great info ¡¡

 

I had a similiar problem (same codes and only after maggie install) after practically tearing apart my Avalanche, The culprit was a vacuum cap in the back of the S/C (on the bend closest to the fire wall). When I was accelerating the cap would stay closed and it was only when i was decelerating to a stop the cap would open slightly and throw codes.It almost drove me to burn the truck, so I would definetly go over everything with a fine tooth comb.You will reap the rewards after it is all done and taken care of. Good Luck. #7

 

**** . . . im getting CODE P1174 < on my NNBS 2 . .. its driving me crazy2 . change my Spark plugs- and code pops up at WOT< . .. how's ur iddle, does it stall all of the sudden, or drop's RPM's?

 

You want your LTFT as close to zero as possible and erring on the negative side. So the range might be -2 to 0 for best case scenario. LTFT of -5 to 0 are acceptable but try to keep them closer to zero. Any lower than -5 or > 5 should be tuned out I think.
Total fuel correction is the sum of LTFT and STFT so the closer STFT are to zero and slightly negative the better.
Negative trims indicate the PCM is trying to pull fuel from being too rich. Positive trims indicate the PCM is trying to add fuel to a lean condition. That is why it is better for trims to be slightly negative and trying to adjust a rich condition rather than one that is already lean. The closer the LTFT trims are to zero the less work the PCM has to command the injectors to perform and the less chance of under or over shooting the goal.