Fix for Check Engine light codes: p0401, po171 and po174
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...
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...
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!
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!!!
Great thread Jewler!!!
Last edited by 02oregonedge+; May 31, 2009 at 01:22 PM. Reason: ....
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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Joined: Mar 2005
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From: Wichita, KS
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; Jun 1, 2009 at 11:48 PM.
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Joined: Dec 2008
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From: Williamston, NC
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.
i don't have a K&N i plan on going to pick up some MAF cleaner tomorrow, and going from their
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.
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.
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.
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.
