P0401 Can’t narrow down the problem
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Junior Member
Joined: Sep 2019
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P0401 Can’t narrow down the problem
Hi guys,
Ive tried nearly everything, but can’t seem to get anywhere. I’ve got a 2008 f150 with a 4.6. The truck started running like hell and then eventually started cutting out in traffic. Hooked it up to the tool, started throwing P0401. Replaced the DPFE, the EGR valve, cleaned out the throttle body and plenum and still can’t get the truck to run worth a damn and it still keeps throwing the P0401. Concordantly, the truck runs fine at idle and in park, but as soon as I get it on the road it start running rough and feels like it’s misfiring and bank 2 starts running like hell- approx 18-24 on the lngtrm. I don’t know if the 2 issues are connected. Any help would be appreciated guys. I’ve dug thru the forum as much as I could and I don’t see a truck on here either the same EGR setup so I’m not sure if that could be a difference.
Ive tried nearly everything, but can’t seem to get anywhere. I’ve got a 2008 f150 with a 4.6. The truck started running like hell and then eventually started cutting out in traffic. Hooked it up to the tool, started throwing P0401. Replaced the DPFE, the EGR valve, cleaned out the throttle body and plenum and still can’t get the truck to run worth a damn and it still keeps throwing the P0401. Concordantly, the truck runs fine at idle and in park, but as soon as I get it on the road it start running rough and feels like it’s misfiring and bank 2 starts running like hell- approx 18-24 on the lngtrm. I don’t know if the 2 issues are connected. Any help would be appreciated guys. I’ve dug thru the forum as much as I could and I don’t see a truck on here either the same EGR setup so I’m not sure if that could be a difference.
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Junior Member
Joined: Sep 2019
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So, what your saying is that low cylinder compression could be producing low vacuum which is not opening the EGR and causing it to throw the P0401? If so, could I just check the vacuum coming to the EGR for proper suction? Sorry, if I sound plebeian, I’ve never exactly been gifted with vehicle maintenance.
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Joined: Mar 2021
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I am sort of having the same issue. I own a 2005 F150 4.6L. I have a check engine light and lots of codes but my mechanic narrowed it down to an EGR problem (P0401). I have tried everything like you have. My truck has a rough idle with a coughing sound coming from the exhaust. The truck shakes when accelerating and when I get to about 50-55 MPH it seems to loose power. Today while test driving it after cleaning throttle body and plenum, the check engine light even started flashing. It will sometimes stall when decelerating. I also notice white smoke (exhaust gas leak) coming from under the passenger side of the engine which seemed to be from right above the first cat on that side. I have replaced the EGR Valve, MAF, throttle body censor, cleaned throttle body and plenum (made sure to get the EGR port clean), replaced plugs. My mechanics only other guess is to take off the intake and clean the egr ports in there and then replace the gasket since i have signs of a bad gasket. That bad gasket could also be ruining my coils. I'm kind of stuck. Any thoughts anyone?