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Check engine light code P0401 how to repair?

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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

  • 96 Answers

SOURCE: MERCURY 2000 ODB2 CODES P0400, P00A0, P0401

P00A0 is a factory readable only code (i.e. only ford dealers have the computer to read it)
the P0400 is a generic E.G.R. flow restriction code. so yes a dvom (multimeter) and a vacuum pump to diagnose it correctly, also check for loose wires as ford harness connectors are known to fail alot due to crappy phenolic content in the plastic and heat combined they can warp and / or corrode the contacts

Posted on Sep 26, 2008

  • 48 Answers

SOURCE: 2000 Honda Accord EGR Valve Error P0401

-after you change the part you have to reset/clear the code

-this can be done by either:
(1) using the OBD2 code reader that Autozone used OR since option 2 (below) is very quick
(2) disconnecting the battery for about 30 seconds (this will delete all codes/radio presets/etc) but it will also clear the 'check engine' code
-this is what I do AFTER i write down my radio station presets :)

-hopefully the new EGR valve resolves your issue after you CLEAR the code
...but that code just means a an insufficient amount of Exhaust Gas recirculation (pressure difference) used to keep the emissions in check
-if it comes back, then there are a few other fixes to try also

-let me know if you need further assistance
-please remember to rate me `fix-ya`if it works

Posted on Nov 03, 2008

  • 783 Answers

SOURCE: Check Engine Light On-OBD reads two codes P1405 & P0401

It is located on the right front valve cover area. It will be either black or silver and have a 3 wire connector with wire colors BN/WH,GY/RD,BN/LG. It will have 2 rubber hoses going from it and connecting to two metal tubes which run to the exhaust.

Now what sets the the P1405 is.
While driving, the EGR monitor commands the EGR valve closed and checks the differential pressure across the EGR orifice. The test fails when the signal from the DPF EGR sensor indicates EGR flow is in the negative direction. Make sure both of the hoses are hooked up and not damaged.
P0401 sets when:
The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum.
So the DPFE could be causing both codes.
I would also recommend that you take a hand vacuum pump and pump vacuum on the EGR while engine is running and make sure you have a drop in RPM so you know that the EGR ports are not stopped up,they are bad about this too.
As far as the rattling converters this could possibly have an effect because it does use exhaust back-pressure along with vacuum to help open the EGR but if the exhaust is still basically stock this probably won't have enough effect on the back pressure to cause this unless they have stopped up and have so much back pressure it is blowing the hoses off of the DPFE or getting so hot it melts them. You can check this with a vacuum/pressure gage, just hook it into one of the hoses from the DPFE and you should have 1 PSI at idle and 3 to 4 PSI at wide open throttle. Anything more would be a restriction.
If all of this is ok then replace the DPFE.

Posted on Apr 15, 2009

  • 1 Answer

SOURCE: tcs light and engine check light on my 2000 honda odyssey

I had the same code/symptoms a few weeks ago. Dealer did a nice job checking through all the details. Replaced the egr too, but no improvement. Finally found one cylinder not firing correctly (not the same pressure as the other cylinders.) Dealer did a value clean/adjustment, for about $250, and the problem has been gone for about a month now. We are also getting about 15% better mileage.

Hope this helps.

Posted on Sep 09, 2009

SOURCE: I replaced the egr valve and the check engine

When you replaced the EGR valve did you check the EGR passage to make sure it wasn't clogged. Since exhaust gasses flow through the EGR passage carbon builds up on the walls restricting flow which can eventually lead to the code p0401 Insufficient EGR flow.

Posted on Jan 10, 2010

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1 Answer

03 honda civic 1.7L p0401 EGR code.

In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit. Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open Clean out the EGR valve and/or tubing to remove deposits Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model) Replace the DPFE sensor (with a good quality / OEM one)

Read more at:

Sep 19, 2016 | 2003 Honda Civic

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Error code p0401 and p0720

when was the last time the egr valve was replaced ?? could be restricting flow .... to the system... thus clogging up..........
p0401- Insufficient EGR flow
then after replacing it,,, disconnect battery for about 20 minutes and it should reset the system.

Jul 22, 2014 | 2002 Ford Ranger Regular Cab

1 Answer

How much would I expect to pay to have the codes P1781, P0401 and P0700 repaired?

First and last code are transmission related and the middle one is EGR. Is the transmission acting up?

May 18, 2014 | 2000 Dodge Stratus

2 Answers

P0401 error code

Depending on your Year and Model, there are some more prone to this Code than others because of the material used in the intake manifold. Ford and its affiliates switched from Aluminum to Plastic to prevent sooting.

On the old style 4.6L a passage under the Airhorn would clog and prevent EGR flow. Bad EGR flow is a Code 401. It can be a Solenoid valve failing to open, but many times it is a clogged passage as I mentioned. Sometimes a bad EGR has a ruptured diaphragm which can be checked by drawing the Vacuum out of it.

For those engines a simple $10 gasket and removal of 8 screws will allow you to scrape out the valley the passage is in.

So this fix is not real expensive, get parts at common autoparts stores.

Apr 06, 2013 | Ford F-150 Cars & Trucks

1 Answer

Need help trouble shooting 2 codes, P0401 & P0455

Google the codes

Lots to read & study

OBD2 PO401

OBD2 PO455

Think you will a repair shop to smoke the
Evap for the 455

Feb 14, 2013 | 2000 Mercury Mountaineer

2 Answers

Check engine light code P0401 98 Ford expedition

OBD-II Trouble Code P0401 - Insufficient EGR Flow

EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor EGR (DPFE). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR. You may notice drivability problems such as pinging (a.k.a. pre-ignition knock) when the engine is under load or the vehicle is at higher speeds. There may also be other symptoms.

A code P0401 most likely means one or more of the following has happened:
The DPFE (differential pressure feedback EGR) sensor is faulty and needs to be replaced
There is a blockage in the EGR (tube), most likely carbon buildup
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum

Check it and keep us updated. Hope this helps (remember to rating this free answer).

Oct 13, 2011 | 1998 Ford Expedition

2 Answers

Hi there i have 1997 Avalon V6 . the check engine light up # 138 and 401 so can you tell me the name of that two please thnks

Trouble codes are normaly 4 digits with a "P" or "B" before it. I am gonna assume that you meant P0138 and P0401:
P0138 is Oxygen Sensor Circuit High Voltage (Bank 1, Sensor 2)
P0401 is Exhaust Gas Recirculation Flow Insufficient Detected

A code P0138 may mean that one or more of the following has happened:
  • Faulty O2 sensor
  • Short to battery voltage in O2 sensor signal circuit
  • High fuel pressure (not as likely)
Possible Solutions Here are some potential solutions:
  • Replace O2 sensor
  • Repair short to battery voltage in o2 sensor signal circuit
for info on the P0401:

Jul 10, 2011 | 1997 Toyota Avalon

1 Answer

Check engin light code po401 what does this mean.

P0401= Exhaust Gas Recirculation "A" Flow Insufficient Detected
for more info pls refer to this link
this isn't really nothing major to worry about it just a emission code

Feb 27, 2011 | 1998 Toyota Camry

1 Answer

P0401. P0133, P1131- emmision test

Based on what the tech manuals say I would change the DPFE sensor for the EGR Valve, careful not to tear the special silicone rubber hoses that go to it from the exhaust, as a Ford dealer tech I saw these codes allot, and the DPFE sensor was almost always the issue or the hoses going to it.

Oct 16, 2008 | 1996 Ford Taurus

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