I'll just leave this note for anyone with the same issue. Check engine, code P0171, mixture too lean. The cause was that a service technician last week must've checked the air filter, but didn't close the cover correctly. The rear tabs of the cover were not in the slots. Sometimes it truly is the simplest things!

 

You just saved me a load of time and probably money trying to fix this. Your tip has just saved me thanks

 

I am glad that worked for you 2


but>>>
hey Grim one tech to another.. got any idea how that worked?

 

Thanks for the info.
I just changed mine today and had the issue of the cover not seating.
I have no idea how your service tech could not have noticed the problem when he/she changed it.
I too missed putting the rear tabs in slots as it's pretty tight in there plus I didn't bother to actually check how to replace it before doing so.
Without inserting the tabs there was no way I could get the front spring latches to lock without breaking or bending something.
I changed the cabin filter at the same time and the damn mice had been at it but luckily no pish/droppings/nests or other unwanted items.

 

Seen this exact issue before a few times. I'm guessing the design of the airbox, intake, vortexes, flow etc etc is designed so tightly that a partially open air box throws everything out of kilter / spec.

 

I often run Dyno Tests on my Mazda also a 2016 (friends) with open intake air . That means nothing before the throttle body? Never had a DTC. As far as I am aware of there is no perimeter for measuring CFM without % of TB actuated so I am not surer how that anomaly of a simple clip not fastened would cause that. Also on many other platforms the shop often gets broken airbox fasteners as well top box that is not sealing properly and never saw a DTC from an airbox lid . Then there is aftermarket CAI that most all eliminate the factory airbox and use open air cone or the like air filters and that is not an issue either?
Then of coarse I just went out before writing this and test drove a 2016 Mazda 3 and duplicated the condition by popping the clips and lifting and slightly setting aside the airbox lid. Went got some coffee and took the long way back to the shop. Ambient was 83F,coolant 195F, IAT registered 97F, averaged TB% 36%, average MPG 26.4 , miles on test 6.7. NO DTC!!! ???

Well I have to chalk this one up to a rare anomalous DTC.


But my suggestion is for those that did get that DTC my suggestion is clean you MAS,MAP and IAT sensors.

 

To the OP - THANK YOU!

My 2015 CX-5 has been having intermittent symptoms of the engine "stuttering" when idling at a stop light, or when slowly backing out of a parking lot. It happened for several months a couple of years ago, and then went away mysteriously - I thought it might have been a bad tank of gas? It took many tanks of gas before it fixed itself, which I was thrilled about, because when I took it in to the mechanic, they weren't able to reproduce it, and told me it was probably "just cold" (except it would happen both when cold, and after I had driven 60+ miles on the highway...)

Then it started up again a couple of months ago - and was getting worse. Last Thursday I made an appointment for Monday - it was finally happening frequently enough that I figured the mechanic would see it.
Friday morning - the check engine light came on! I was kind of thrilled - A Real Problem!
Saturday morning, I took it over to O'Reilly Auto parts to get the code read - P0171
Started googling to see what I might be in for, and read all kinds of stuff about O2 sensors, fuel injectors being dirty, vacuum leaks.

And then found this post - and as soon as I read it, I remembered - back in May, when I replaced my engine air filter, I *struggled* to get the cover back on - I finally was able to snap the clips on, and called it good - figuring it was closed since it snapped on?

But, after reading this post, I found a youtube video that showed me exactly how to put it back on *properly* - realized that I did not do that - went out and took the cover off, and put it back on per the proper directions.
Turned the car on - the check engine light went off, and I haven't had a problem since! I drove it all over Sunday and this morning - I'm still a bit paranoid, but I'm starting to feel confident that this might have solved it!

 

anyone know if I can solve this by myself? I think my oil cap wasn’t tightened entirely, so when I drove away from my moms house the cap came off and I drove for like 10 miles before the light came on

 

Yes, a loose oil cap can cause the code.
You will likely need a manual reset (scan tool or take to garage or part store that can do it) to get the light to go off as the computer will store the code until it is rest.