Fix for Check Engine light codes: p0401, po171 and po174 - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 05-31-2009
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Fix for Check Engine light codes: p0401, po171 and po174

After talking to Jazz921 and a local Ford tech. I finally found the vacuum line that causes all those codes and a motor to run horrible and get terrible fuel economy. This particular vacuum elbow will throw codes p0401,po171 and po174. My local dealership has about 1-2 4.0 SOHC rangers a week for this same vacuum elbow. It costs about $180 to fix at a dealer. It is a simple fix with only a 7mm socket wrench to fix it. First off take off you 4.0 sohc trottle body cover, then just pull this elbow off and examine it. Replace if needed. My truck went 100 miles today trouble free and code free for the first time in 6 months. I HIGHLY suggest you replace these. This little part causes a whole lot of problems and is very cheap and easy to fix.

Check engine light codes:
p0401- Insufficient EGR flow
po171- Lean bank 1
po174- Lean bank 2


Ford part # F8UZ-6762-AA - $15.00

Then disconnect your battery for about 5 minutes to clear your codes. reconnect and let idle for at least 5 minutes.

Pics of this little devil. It is under your radiator hose...

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Old 05-31-2009
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Its funny how one little thing can cause so many problems. Oh a trick to resetting codes is after you unplug the battery just turn the headlight switch on for 10 seconds and that will clear it too and you won't have to wait around.
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Old 05-31-2009
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Quote:
Originally Posted by 04blackedge View Post
Its funny how one little thing can cause so many problems. Oh a trick to resetting codes is after you unplug the battery just turn the headlight switch on for 10 seconds and that will clear it too and you won't have to wait around.
you are awesome Trent! Good advice!
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Old 05-31-2009
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Same thing happend to my truck.. I didn't figure out it was the vaccum line until I replaced both o2 sensors, then realized it was that stupid elbow, doh..

Great thread Jewler!!!

Last edited by 02oregonedge+; 05-31-2009 at 02:22 PM. Reason: ....
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Old 05-31-2009
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Glad I could help and glad your truck is working great again!
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Old 05-31-2009
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Glad to see you got it fixed.
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Old 05-31-2009
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Good, my mom's exploder is throwing the same codes. I will have to look on hers now in that area.
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Old 05-31-2009
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Quote:
Originally Posted by Toreador4x4 View Post
on the right side of your intake, there is a vac line that runs from the back of the motor to right by the throttle body, the upper radiator hose rubs on this elbow and rubs through. get a can of carb clean when the motor is running, idling, and see if the rpm changes depending on where you spray. spray around that line or remove it and inspect it and see if there is a problem with it. this would cause your lean code but im not sure about your EGR code, could be the DPFE sensor if i had to guess
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Old 05-31-2009
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andddddd tonight i broke a plug wire. LOL
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Old 06-01-2009
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Thanks Ben for the pictures. Mine has the same problem but the hole is underneath. How hard was it to get off? I got the left side of the tube but can't get the right side to budge.

Last edited by soccerjohn; 06-02-2009 at 12:48 AM.
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Old 06-01-2009
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What a coincidence, my truck has been throwing the PO171 one recently, but it seems to be getting better gas mileage? Seriously. And it only throws the code when I have my truck in 4wd, and the motor is loaded.
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Old 06-01-2009
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Lol mine pulled the p0171 code at the dunes this is way to convenient !
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Old 06-01-2009
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Hopefully you get that 16+ mpg that you should be getting. I consistantly get 17+ so there is no reason why you shouldnt.
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Old 06-02-2009
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LOL... check your elbows...and the line next to the fender well on drivers side...
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Old 06-02-2009
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Mine is missing that elbow

glad you got her fixed. Justin FTMFW!
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Old 06-02-2009
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ace, keep in mind also that only having one bank lean may not be a vacuum leak, it could also be a bad or dirty MAF. do you have a k&n?
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Old 06-02-2009
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beard that is a SWEET *** avatar
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  #18  
Old 06-02-2009
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Quote:
Originally Posted by Toreador4x4 View Post
ace, keep in mind also that only having one bank lean may not be a vacuum leak, it could also be a bad or dirty MAF. do you have a k&n?
i don't have a K&N i plan on going to pick up some MAF cleaner tomorrow, and going from their
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Old 06-02-2009
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THAT is _exactly_ the piece that went bad on my truck, a few months ago. the truck was running like crap at idle, nearly (and, in two cases, actually) stalling at traffic lights, etc. I never got any sort of check engine light, nor any codes... just the running like crap portion! the part # from Ford actually replaces the entire assembly, not just that elbow, and costs about $30. My dealership (mind you, not the one I bought the truck from!!) installed the part for free.
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  #20  
Old 06-09-2009
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had mine throw the same codes, but it turned out to be the fuel regulator.
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  #21  
Old 06-09-2009
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how do you know it your truck is throwing codes and what codes they are? im guessing when the CEL comes on you take it to ford or someone w/ a computer and hook it up.
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Old 06-09-2009
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Quote:
Originally Posted by shawn '93 View Post
had mine throw the same codes, but it turned out to be the fuel regulator.
yeah, when that diaphram in the fuel preasure regulator rips, it sucks gas into your vacume system and messes things up to but I hadnt heard of it happening on the SOHC, just the pushrod 4.0s.
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Old 06-09-2009
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Is that elbow supposed to suck flat when the truck is running? My truck isn't running funny or stuttering or anything but it sucks that elbow flat.

Is the new elbow you got sturdy enough that it doesn't suck flat when the truck is running? It just seems that it would have better flow/suction with it opened up.
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Old 06-09-2009
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If it's going flat you need to change the elbow, or it's going to do what mine did and get a hole in it from too much heat..
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Old 06-09-2009
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for sure elbow change time, if its that weak its gonna start to leak really soon.
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