Code P0171
 

Hey guys! I’ve been running a p0171 code - system running too lean bank 1 - for a while now and I can’t figure out what’s causing it. I have an aftermarket intake and I replaced the MAF sensor already but that didn’t fix it. Subaru looked at it and didn’t mention a leak or anything so not sure why the AFR is messed up. Could a dirty air filter be causing it?

Also could someone explain what “bank 1” refers to? Somebody said it refers to the first o2 sensor but my knowledge is limited when it comes to this since this is the first time my car has been running lean. Any tips would be appreciated since I really don’t want to damage my engine:bonk: