I'm getting a bank 1 too lean error code, I first tried to clean the MAP sensor which worked for a little bit but the codes came back. Now I am getting a winning noise from the engine bay. it has about 84k miles on it
please let me know if you have had any experience with this

 

bank 1 is the default for I4 and I5 engines, which is telling you you have too much air in your fuel trim. Typically this is caused by air leaks and not by a failed or dirty sensor, particularly in a newer car (I'm not sure if you meant to say you cleaned the MAF sensor). Start by inspecting vaccuum lines, intake air hoses etc and spray around (you can use that MAF cleaner you bought) to see where any fluid gets sucked in and bumps the idle. It can also be caused by an exhaust leak upstream from the O2 sensor so listen around for any sounds. If you can't find an intake air leak visually, you can have a shop do a smoke test.

 

I would look at everything MT6127 suggested above as he clearly has a lot of experience on his side. We experienced the "Lean on Bank 1" condition with our S60 and it was accompanied by the check engine light that would stay on for a few days then go away for a few more only to come back on. It turned out to be the oil trap (equivalent of PCV) in our case. Once that was replaced all was well with the world again.

 

Good point about the PCV system - its using the intake vacuum to pull the blowby gasses out of the crankcase into the air intake. the oil separator has a diaphram in it which can tear and that can allow too much air into the intake (creating a lean condition with whistles and other symptoms) and worse can pull some of the oil from the separator as well, messing up the MAF/throttle body etc. Good news is on the new models the oil separator is a lot more accessible than say on the 850s/V70s etc from the 90s/00s. I believe IPD also sells a repair kit to replace the diaphram for about $15 as well. If you hear any odd whistling noises, try removing the dipstick or opening the oil fill cap to see if the sound changes.

 

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This is for the 5 cylinder. I saw this not too long ago as I was debating whether I needed to as maintenance do the PCV on the C30.
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https://www.ipdusa.com/catalog.asp?C...gorycrumbs=986
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This video was very helpful.
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