2003 Ford Windstar P0171 and P0174, Banks 1 & 2 Lean

This 2003 Ford Windstar came in with the service engine soon light on. Checking code revealed codes P0171 and P0174, banks 1 and 2 lean. I checked for vacuum leaks and none were found so I moved on to the Mass Air Flow sensor. It is common for them to get dirty and cause these fault codes. The MAF sensor is located inside the air filter housing so it had to be removed. I loosened both hose clamps and pulled the rubber boot from the throttle body and then from the air filter housing. Then I unlocked the spring clamp that holds the two halves together.

The crankcase ventilation tube also had to be removed from the rubber hose and more importantly it has to be put back in place during assembly. You can see it just to the left of the master cylinder.

After unhooking the wiring harness connector I took the housing to the bench for dis assembly. There are several locks that have to be released. I used a common screwdriver blade to pry them inward while pushing the sensor out from the other end.

There is also another wiring subharness that has to be removed. It is kind of a pain but I take my time so as to not cause any damage. Once the two halves were separated I removed the sensor from the housing using and tamper resistant torx bit socket.

This is were the actual sensor elements are located and in most cases you will find a build up or film on the element. I use a pick as shown or a small screw driver and very lightly rub the film off. Sometimes if it is heavy it will lift off in one try but most of the time it takes a little while of very light rubbing to remove the film. Some people use cleaners but I prefer to manually rub it off so as not to cause and damage to the sensitive parts. Many cleaners will damage the plastics.

Expedition 33

Just several different pictures of the same sensor. There are two elements inside and the most problematic one is the one further inside that you cannot see.

This is just one of the possible causes. There are many and one of my readers left a link to a repair site that has more answers on this problem.

Ford has a TSB out on this for 1999 to 2003 Windstar. if you want to do it yourself, you need to go to your local parts store or dealership and ask for a “Valve cover repair kit”. This site link gives step by step instructions for the fix.

55 discussions on “2003 Ford Windstar P0171 and P0174, Banks 1 & 2 Lean”

  1. Thank you for your response regarding my 2003 Ford Windstar, how would you know if you have a vacuum leak? My heating, air conditioning & cooling system is fine. What do you mean low fuel supply and how would you know if you have a dirty fuel filter or faulty fuel pump what should I look for? Is there a way to see if the MAF sensor is faulty? Thank you again….

  2. There are several things that can cause dual lean codes on these vehicles other than a dirty MAF sensor. Among which are vacuum leaks, low fuel supply caused by dirty fuel filter or faulty fuel pump and of coarse a faulty MAF sensor instead of just a dirty MAF sensor. If you can email me with more specifics about your problem I will try to help.
    info@the-electric-connection.com

  3. My 2003 Ford Windstar has a code P0171& P0174, I did everthing you mention clean the MAF sensor. I turn on the van the check engine light is still on can you please help me…Thank you

  4. 2005 Ford Windstar

    Thanks, I’ve been dealing with P0171 & P0174 over the last 6 months and have spray cleaned the MAF sensor a few times but after reading your post with the great great photos and text I took another look at the sensors under magnification and sure enough I could see the build of dust like crud on the sensor on the air flow side. All my spray cleaners in the past didn’t remove it until I touched the sensors (2) front and back (can only see the back on fron down the tube) one with a Q-tip with alcohol the crud came right off and the sensors cleaned up like new but only could I see this under a jewelers loop magnifier and under a light. When you put everything back don’t forget to attach the vacuum tube to the backside of the air cleaner housing, easy to forget.

  5. Thank you, Thank you, Thank you.
    This was my problem exactly. I probably saved hundreds just by cleaning that sensor (I guess it is really two sensors in one housing). As I did not have the correct anti-tamper skrew bit, I undid the bolts that went into the plastic part containing the metal screen. It gave just enough room to clean the sensor. Thanks again!

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