This is so far the best article I have seen on the ecu seeing an implausible condition and coding out.
Bottom Line - its one of those things and requires a tune to fix.
this can explain the randomness -paraphrasing my understanding here:
"Some people have the benefit of better Air pressures where they live blissfully inside the compensating window of the ecu while using a modified intake.. Others have a variability in the environment for baro and this can exceed the set limits of the ecu to compensate more easily".....
The MAF is active in steady state driving, which is Not during warm up and during transients. Transients are like during shifting up or down certain hard accel and decel moments and the ECU then refers to a table to manage gas Air to Fuel - AFR.
The VVE table is calibrated to the stock Intake calibration. This is the Volumetric Efficiency table. GM tuners avoid tuning it. Ford uses the table as the primary AFR calibration as they are SD Tuned and GM is MAF (primarily) tuned for AFR, and looks to SD for help during times where air flowing across the MAF is turbulent. MAF is supposed to be a more finer tuned, sensitive, architecture.
ECU looks to VVE for a moment and finds an implausible condition to satisfy resulting in an alert/code/mil/cel.
I don't know what the weather is in Sunny FLA today but we have finally gotten a good layer of frigid air settling in NH.
Like COOPER said, it just may be that model of intake is more trouble than its worth to pursue a tune and all that goes along with it.
https://repairpal.com/obd-ii-code-p0171
A couple of logs to see it... T marks the transient
Here is my Fuel Trim Table and it is need of me going and doing a Recalibration of the MAF after I did some MOD. The recommended variance is +/- 5 percent. So I need to go and tune the MAF.
