Hello,
2012 Mazda 3. Recently i have had a P0171 ( System Too Lean Bank 1) code thrown on my car. When pulling the reading the code is being thrown 3 times. I have reset the code and all was normal. The check engine light came on again today after a long drive, and then idling for about 5 minutes. Being that the check engine light does not come on all the time is confusing. Recently my mass airflow sensor went out, and I replaced it. Looking around a bad MAF could be the cause. Maybe it went bad? Any ideas here? I understand spark plugs being bad would cause a too rich, not too lean message. The car run perfect from my perspective. Thanks

 

Update. I sat at a red light, engine had a rough patch for about 1-2 seconds, i would describe how it gets a tad rough just for a moment when the AC compressor turns on , and the check engine light came on with the code again. Just so weird its super random and not always popping on. I can go a couple days without it coming back on.

 

There is a specific dignostic tree to solving this issue.
First STO cleaing the DTC. If you looked you have seen that it is in the pending file and all you did was turn off the dash light!
You should slop to speed the fact finding problem solving to check your ECU monitors to see which emissions are effected.
The reason the DTC keeps returning to the dash check engine light is because you are cycling the engine. The ECU is trying to resolve the issue obviously it will need a part failing replacement.
The first thought is when the last time you cleaned the following
MAP
IAT
T/B
AF

Then when was the last time you changed your spark plugs

Look at the tail pipe on the next COLD START, is there water vapor and droplets dripping out the tail pipe.
And what does the tail pipe look like. You may wipe it clean and see what appears again after a few days or about 100 miles?
Your H02 may be dirty or worn out and not communicating the correct information to the ECU?

And the list goes on......

 

How did you handle the issue ?

 

It not so much how someone handled the issue as it is to follow a proper way to determine the cause.