P0172 and P0505 Codes with Freeze Frames - Please Help

Clean your MAF and throttle body then unplug it reset it plug it back up and go for a drive and see if that clears you up.

 

The P0172 seems to be older news. You only saw it once, and both the short- and long-term fuel trims in that freeze frame were awful, but they haven't seemed nearly that bad since. If nothing was done to correct it, there might be a bit of mystery how it got better, but we can probably set that aside for now and focus on the P0505 codes, because those are getting kind of insistent.

P0505 is a code about not keeping the target idle RPM reliably. There is nothing in the workup for that code to suggest that replacing the MAF sensor would even be a part of that workup; the Usual Suspects appear to be air intake leaks, the throttle body, or the ECM.

There are two criteria that can set the code: one is the actual idle RPM going below target by 100 RPM or worse, or above target by 150–200 RPM or worse, 5 times within a single trip.

The other is the learned idle air volume (to achieve the target idle) coming out either implausibly low (less than 0.6 L/s) or implausibly high (more than 4.5 L/s).

Weirdly (to me), none of these P0505 freeze frames shows what looks like a smoking gun for why the code was set. They all show the engine turning within 52 RPM of 1000, which I kinda thought was the target for the warmed-up idle speed, and the coolant temperature shows warmed up in all three cases. Maybe I'm misremembering what the gen 2 target idle RPM is.

Using the indicated air temperature, MAP, and MAF, the air volume is working out to something around 2.3 L/s in each case, which could hardly be more squarely in the middle of the acceptable [0.6, 4.5] range.

So that's a little funny. I was expecting the freeze frame to show something more glaring.

 

While agree that the fuel trim values don't seem as bad as shown in the P0172, they are outside the +/- 10% that mr_guy_mann likes to see, so I agree with Tom that unplugging the MAF, removing and cleaning it, and also cleaning the throttle body would be something worth trying. Put it all back together and see how it goes If you get the engine failing to start or running roughly, disconnect the 12 V battery for a minute to reset the EMC to factory defaults. Then go for a drive to see if that helps improve things.