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Old 06-01-2009, 07:46 PM   #1
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Default P0401 EGR low flow code

just got my 01 ex running and EGR low flow, p0401, is coming up as a hard code. i clear it and it will come back on in a day or so when the moniotrs reset.

(tried searching EGR, p0401, and 401 so dont post saying to search)

i do need the CEL off since i will be goign to emissions very soon.

what is the procedure to diag this code? any common symptoms or areas that i should be concered about?

im not a work so i cant check napafix or alldata or mitchell but just wnated to get a heads up since sometimes this site is actually more useful then mitchell, alldata or napafix.
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Old 06-01-2009, 11:09 PM   #2
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Default Re: P0401 EGR low flow code

allright..i will jsut clean everything including taking off that ain in the butt intake manifold...those 4 bolts under the manifold are such a pain to put back on.
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Old 06-02-2009, 11:05 AM   #3
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Default Re: P0401 EGR low flow code

1. The most common problem is plugged EGR ports. If manually operating the EGR valve, the engine should stall at idle. To manually operate the EGR valve (unplug the EGR valve), power the terminal on the EGR valve that the Blue/Red wire goes to and ground the terminal that the Black wire goes to.

2. The valve should operate and the engine should stall at idle. If the engine does not stall, the EGR passages are restricted with carbon and will need to be cleaned out.

3. When the EGR valve is operated, always verify that it will open.


Potential Causes: Restricted Exhaust Gas Recirculation (EGR) Passages
Exhaust Gas Recirculation (EGR) Valve

Tech Tips: The EGR valve is on the side of the cylinder head and flows into the cylinders or flows into the injector spaced plate. The intake manifold will need to be removed to correctly clean out the EGR passages.

Diagnostic Codes: P0401
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Old 06-06-2009, 02:00 PM   #4
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Default Re: P0401 EGR low flow code

UPDATE:

well..i think i found my problem. i did apply power and ground to the egr valve and you could hear it click. also the engine did not stall and no change in rpm when i manually closed the valve.

i took off the intake manifold again and my intake manifold gasket did not have a hole for the EGR routing from the head to the intake manifold. i oprdered the gasket kit from ebay so my fault. i drilled an opening in the intake manifold gasket itself right where the port is to allow the EGR gases to the intake manifold. we will see if this helps.

now i am just concerned with the head gasket i got from ebay's kit. i hope it isnt blocking the oil orffice for the vtec oil passage. i think that would throw a code for vtec no?
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Old 06-07-2009, 01:11 PM   #5
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Default Re: P0401 EGR low flow code

well...i cleaned the intake manifold portion very well...good enough to lick it and resetted the ecu. code came back on in 3 trips. back to the drawing board!!

anybody have the whole egr routing diagram? 2001 civic ex.
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Old 07-12-2009, 10:31 PM   #6
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Default Re: P0401 EGR low flow code

ah.. forgot to update. my bad.

turns out i was half right with the drilling of the big hole on the gasket itself. i ordered a new gasket for an ex and the new gasket came with the big hole already open along with 4 small holes for each chamber.

turns out i got the wrong gasket kit from ebay. i eneded up selling the car and the car is all good now. no CEL and runs just fine with emissions.
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Old 06-28-2010, 07:06 PM   #7
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Default Re: P0401 EGR low flow code

The same thing is wrong with my '04 Civic VP. The original engine that was in the car seized up while under wanrranty. My honda dealer replaced the engine with a remaned engine got the car back drove to the house the MIL pops on. I take the car back the next day they told me DTC P0401 so they replaced EGR and gasket with a new parts gave it back to me not even a month later the MIL pops back on. I check the code its DTC P0401 so i take it back again different Service Advisor this time. They again tell me DTC P0401and replace the EGR and gasket with new parts. I get the car back and a few days later the MIL comes on again and its the same DTC P0401 & DTC P0404 (EGR Valve Insufficient Lift) so by now im sick of the dealer going through the motions and not fixing the problem. So I have a friend that was a Honda Tech so I take my car to him and we diagnose that its not a bad EGR by applying current voltage to it while car is on but not running. We also test all the wiring going to and from the EGR for a short and also to verify the correct voltage is where it should be. And it was so we remove the EGR valve and inspect the passage and intake manifold for blockage nothing. So back to the dealer it goes 2 weeks later the dealer tells me that the intake manifold and water passage and all gaskets and o-rings need to be replaced But that its not coved under the warranty due to the carbon buildup and itll be $1150.00.
So I tell them im not paying that im picking my car up tommorrow have it ready!! So now 13 months later and my reg is due and its mandatory smog in California every other year. So now Im screwed took it to honda dealer again and they charge me half price just $70.00 to clear the code i asked if they test drove it he said yes i asked did u get on the freeway he says no. I tell him test drive on the freeway he declines. So off i go to pick to pick it up and get on the freeway just to have the MIL come back on so i go back to the dealer they check and recommend replacing the EGR valve i tell them im not paying $370.00 for the same fix that didnt work the first 2 times. So what i really need is the wiring diagrams from Mitchell On Demand for my car. My friend got a copy of AllData wiring diagrams for my car but he says they are not thorough enough. Hes positve it is another cause for the MIL and suspects another sensor or system is just passing the code to the EGR. This was after we had cleaned out the intake manifold thoroughly. I think it is the ECU does not like the reman engine for some reason. Can anyone help.

THNX
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