Po171 bank 1 system too lean

Although the 4 cylinder engines have only 1 bank - it is also known as bank 1 .. One of the reasons to post which engine is in the vehicle is for more accurate answers - there are different possibilities for each engine!

Possible causes : Intake air leaks - Faulty front heated oxygen sensor - Ignition misfiring - Faulty fuel injectors - Exhaust gas leaks - Incorrect fuel pressure - Lack of fuel - Faulty Mass Air Flow (MAF) sensor - Incorrect Positive Crankcase Ventilation (PCV) hose connection Read more: http://www.autocodes.com/p0171_ford.html ▪️IF V/6 > Bank # 1 is back side - nearest firewall ▪️