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 Tech description If the P0171 is combined with the P0174 code, it’s very likely that…