Can a bad spark plug cause P0171?
Can a bad spark plug cause P0171? Can bad spark plugs cause p0171? - Quora. Not likely. A P0171 ( too lean, Bank 1 ) code is most often caused by a vacuum leak downstream from the MAF sensor or a malfunctioning MAF sensor. Bad spark plugs could actually cause the opposite code ( too rich, bank 1). What to do if check engine light code p0171 is triggered? If check engine light code P0171 is triggered again, check the rest of the vacuum lines for leaks and continue to the rest of the diagnostic process. Remove the mass airflow...