According to my 2009 shop manual dtc2179 is 'lean at cruise', not 'lean at idle' (which is dtc2189). Either way could be a lot of things related to improper fuel delivery and/or vacuum leak. Also could be 'skewed' MAF sensor or maybe O2 sensor. Former might not show MAF dtc but latter should also show O2 dtcs. I would look for vacuum leak, beyond that may need scan tool for detailed diagnosis. Good luck.