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Po171 bank 1 system too lean

(1999 Ford Contour)
in Lancaster, PA on February 14, 2018
The check engine light code on a 1999 Ford contour reading po171 bank 1 system too lean. What should I check
What seems to make the problem better or worse? None
How long have you had this problem? One day
Tags: nothing seems different, ford, contour
Displaying 2 answers & 2 comments
Popular Answer
on February 14, 2018
4 cylinder OR V/6 ?
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on February 14, 2018

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!
on February 14, 2018
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

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▪️IF V/6 > Bank # 1 is back side - nearest firewall ▪️
on February 14, 2018
If you have a four cylinder you are going to want to start with fuel pressure and checking for vacuum leaks. If you have a good scanner that can read live data you can look to see if the oxygen sensor is switching properly too. It's possible you just have a bad oxygen sensor.

In any case hands on inspection is needed to pinpoint the exact cause. Here is a link to find a shop near you.
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