P0171 code + incomplete emissions

Okay, folks, I kinda know where I'm trending here, but I wanted to get some other ideas.

My 3.4L has ~130k miles, As I was driving back home this morning, the CEL came on. Ran the code and it was the P0171. I also notice several emissions readiness circuits were incomplete.

I just replaced the vacuum lines a couple weeks ago with silicone lines, so I have my doubts my P0171 is from a vacuum leak.

The next obvious answer is the MAF. I took that out and gave it a good cleaning, there was some small debris inside, but nothing too bad (it's original to the truck, and I've cleaned it once before several years ago).

The below Torque Pro screen caps are from right after reinstalling the freshly cleaned MAF. There were these codes upon startup.

I happened to glance at the emissions readiness screen too, and there are a few "incomplete" sequences related to the O2 sensor.

I've just cleared the codes, but I haven't had a chance to take it back out for a test drive to see if the codes come back.

So this kinda makes me think the o2 sensor is at fault, although the 0113 and 0171 can be caused by a bad MAF sensor, too.

Thoughts?

 

There’s a way to check if the O2 sensors are working - even what voltage they’re sending if you can backprobe, but I know there isn’t a lot of room in there. You could backprobe the MAF too. Can you get MAF live data? My Foseal with Car Doc does I think. Knowing that you just raised your vehicle a quick visual to check if the O2 wires are jammed or broken could be a good start if you haven’t already.

https://youtu.be/NKsS6AELPuM

here’s a tangentially related video where South Main does some diag on a 5vz. Seeing how he can’t quickly open the hood gives a chuckle and identifies how long ago rust made these trucks extinct in upstate NY

https://youtu.be/1uEGor5IUnY

 

I'll double check the wires, thanks

MAF was showing 3.3 (after cleaning) at idle.

 

@mechanicjon ?

 

So I did just back from the test drive. About 20-30 minutes of city and freeway, and everything seems fine. The evap and cat still haven't cleared, but the O2 sensor ones did. At least so far the code hasn't come back.

It think what may have thrown me off was that the last time I cleaned the MAF, it was far dirtier than this time, and it never threw a code.

I did just clean/oil my K&N air filter yesterday, so I wonder of some of the oil fowled the MAF. It's never done that before but I guess anything is possible...

 

I had the same code and did a smoke test to check for vacuum leaks and couldn't find any. ended up replacing my maf, both 02 sensors and 4 new spark plugs and it went away. I have the same app and obd2 sensor I can send you screenshots of my data If that would help? probably not telling you anything you don't know but lean code is from your stft and ltft adding to over or under +-15. normal range is supposed to be +- 10. before changing maf and 02 sensors I was at 17.5 stft and 28 ltft. now I'm at normal values.

 

the evap drive cycle will not start unless certain conditions have been met. The fuel tank MUST be between 1/4 and 3/4 full. The coolant temp sensor MUST be within 10 degrees of the air temp sensor with an 8 hour time frame and this must happen twice. In english this means that the truck has to be cold started twice from an over night sitting 2 times with 1/2 tank of fuel and then the evapoartive drive cycle will start. The catalyst one is different. I can drive on the freeway and do city driving and it wont run and clear until I descend a long hill with either a slight or zero throttle. Your experiences might be different.

 

Yeah, the catalyst ones are always a PITA to clear - they take forever it seems. The O2 ones cleared on my last test drive, and there are no more pending codes. Unless it takes longer for ~30 minutes for the 0171 code to reappear, it seams like cleaning the MAF did the trick.