P0171 FORD - where exactly is the front O2 sensor located on a 2004 Ford Expedition 5.4L?
P0171 Fuel trim lean bank 1 Bank 1 is where cylinder number one is so you need to go there,and to begine with this is a lean bank code,so look for a vacuum leak especially at the PCV valve that will affect bank 1, also sparkplug condition this will give off a lean bank code.partially plugged injector (most unlikely)
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