Check engine light comes on and off, auto zone test read back EGR flow insufficient/manufact.specif.DTC/see service manual.what does any of that mean?HONDA ACCORD 4CYL.2001

diagnostic aids:
a vacuum restriction to the map sensor--a skewed map sensor reading can cause the PCM to read an incorrect MAP change during the EGR flow test
an engine that is running poorly due to mechanical condition such as worn piston rings, ect. can cause low engine vacuum thus EGR flow test will fail
excessif backpressure of the exhaust system can cause P0401
exhaust system leak can cause an insufficient amount of EGR flow
a restriction in the intake manifold such as carbon deposit and casting flash.

NO YEAR, STATED.
NO ENGINE STATED.
now that makes this hard, no? my only clue is the body shell.

why not post the DTC error , not your interpretations?
on newer cars there are up to 5 or more EGR DTCs.
the exact dtc or the lack of some , tell the FULL STORY.
for example on newer cars there is EGR feedback readings.

btw: i own a 04GV and have 100%+ documentation on it and can fix any EGR fail on any car made, sure can. GEN1 , to GEN now.
but need more INFO.

po300 random misfire po401 low flow egr p1404 egr. check spark plugs and check for vacume leaks. with the po400 1404 could be your egr valve is good but po400 means low flow which to me indicates that the egr passage may be clogged up and needs to be cleaned out check out scottykillmer.com the passage way may be easy to clean depending on the position of the egr vavle but you might have to remove the intake manifolld

code P0401 is an EGR code.
which is insufficient EGR (exhaust gas recirculation) flow.it is quite common for people to just replace the EGR valve.



You can try doing it your self.:----
To troubleshoot these issue and solve it yourself.I suggest you to go through few help links related to
OBD code P0401:-----
Click the link below:-----

1997 Chrysler Sebring: OBD Error Code P0401?

http://howtobyme.blogspot.in/2012/06/1997-chrysler-sebring-obd-error-code.html

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2004 Hummer H2: OBD Code P0141?

http://whoisbyme.blogspot.in/2012/06/2004-hummer-h2-obd-code-p0141.html

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DTC Trouble Code P0401?

http://schematicsdiagram.blogspot.com/2012/01/dtc-trouble-code-p0401.html

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These will help.
Thanks.

What code ? are a few different ones for EGR valve > Low & high circuit voltage , testing circuits , PCM testing etc.... no code tells you to replace the EGR valve without testing . Your best bet , take it to a qualified repair shop.
DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient
DTC P0403 Exhaust Gas Recirculation (EGR) Solenoid Control Circuit
DTC P0404 Exhaust Gas Recirculation (EGR) Open Position Performance
DTC P0405 Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage

You should be fine. Usually what happens is when such a part causes the light to go on, the light will continue to come on again a few time after replacement of the part.

Simply disconnect the battery and let it sit for about 1minute (oat least 30 sec). Then reconnect the battery.

Drive the vehicle and if the light still comes one, take it to an auto parts dealer that can do a diagnostics test and ask them to clear the codes.

Even after this the light may come on - drive for about a week more and if it still stays on, then have the test done again and replace any other part that any codes may present faulty.

Otherwise, sometimes it itakes the computer and engine to adjust to the new part and get an accurate (consistant) reading until the light will stay off.

A lot of the time a light will come on if the O2 sensor(s) are bad. This isnt' a huge issue right aways, will slightly affect feul mileage and the amount of exhaust return into the engine for being reburned. Replace these if necessar (and if affordable).

Please let me know if you need any further assistance.

carsandcomps,

Guru, Premium Expert @ Fixya.com

did u try cleanning out the lines connected to the egr they usually have a lot of hydrocarbon build up

Specifically DTC P0401 is "Exhaust Gas Recirculation (EGR) Insufficient Flow". Now this is where we have to be careful when we read a code. In this case it is not saying the EGR valve is bad, it's saying the EGR flow is too low. Now it could be because the EGR valve is bad. Or it could be a clogged EGR tube or a broken vacuum line. This is why you have to be careful and check the whole system before you go changing parts. The PCM tests the EGR system during deceleration by momentarily commanding the EGR valve to open while monitoring the Manifold Absolute Pressure (MAP) sensor signal. When the EGR valve is opened, the PCM should see a proportional increase in MAP. If the expected increase in MAP is not seen, the PCM notes the amount of error that was detected and adjusts an internal fail counter towards a fail threshold level. When the fail counter exceeds the fail threshold level, the PCM will set DTC P0401. The number of test samples required to accomplish this may vary according to the amount of detected flow error. Normally, the PCM will only allow one EGR flow test sample to be taken during an ignition cycle. To aid in verifying a repair, the PCM allows twelve test samples during the first ignition cycle following a scan tool Clear Info or a battery disconnect. Between nine and twelve samples should be sufficient for the PCM to determine adequate EGR flow and pass the EGR test. To check the system first you need to remove the EGR valve and if it is clogged or broken. If it is, clean or replace it. If it is okay, then remove the EGR inlet tube from the exhaust manifold and the EGR outlet tube from the intake manifold. If either or both are clogged, clean them out or replace them. Then check the ports in the manifolds themselves to see if they are clogged. If so, clean them out. When you are done, disconnect the battery for about 30 seconds to clear the code and drive the car to see if the light comes back. This should take care of the problem. If not, then you will need to put a scan tool on the car and see what the EGR control system is doing wrong and correct it.
The Valve on this car is electronic, so, unfortunately a vacuum pump will not work for testing.
If you have a scan tool, you can command the pcm to open the valve to see if the valve itself is working.There are really only4 things to go wrong with these things, PCM, wiring,the valve itself, or plugged passages. I have never seen the pcm cause this problem, or the wiring for that matter. If you say you have pulled the EGR and checked the intake passages, then I would be pretty confident in saying the the egr valve itself is bad.
Thanks for using FixYa - a FixYa rating is appreciated for answering your FREE question.

Insufficient EGR Flow Detected

Possible Causes:
DPFE sensor signal circuit is shorted to ground
DPFE sensor VREF circuit is open between sensor and PCM
DPFE sensor downstream hose off or plugged
DPFE sensor hoses both off, loose or damaged
DPFE sensor hoses connected wrong (reversed)
EGR orifice tube is damaged or restricted
PCM has failed
And what sets the code is…….Engine started, engine running in closed loop under steady cruise conditions, and the PCM detected the DPFE sensor input indicated insufficient EGR gas flow. Run the KOER Self-Test, and if DTC P1408 is present, the fault is currently present. This code sets in 2 Trip(s). The light will stay on until the cause is repaired. A bad EGR valve is only on possible cause.

Hope this helps,

Dave

The DPFE (Diferential Pressure Sensor)sensor is usually mounted on the engine and is connected to the pipe that runs from the exhaust manifold to the EGR valve with two rubber hoses. When the sensor goes bad, the Check Engine light comes on and typically sets any or all of teh following fault codes: P0171 & P0174 (lean codes), and/or P0401 (insufficient EGR flow). Nine out of ten times, the fault is not a bad EGR valve or a vacuum leak, but a bad DPFE sensor. A replacement costs about $112 at Ford, or about $48 at an aftermarket auto parts store.I hope this helps.