Question about Ford Crown Victoria

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P0401 exhaust gas recirculation flow

What should i do

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This is very common. There were some production years which used an intake manifold subject to accumulating soot in the EGR passages. Because of the location of the sensors, the wrong part is often blamed for this problem.

All you need to do is remove 8 bolts holding the metal airhorn to the intake manifold plus the intake air assembly. Under the mounting plate there is a channel shaped like the letter C with a center notch in it. Clean this channel out with a screwdriver or anything you like.

Use a new $10 gasket and reassemble. Clear the computer and it should be good to go.

Posted on Oct 17, 2013

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Try cleaning it first clean out with dp oil in a can leave to drain out and refit. one times works as they can get clogged up. take it off. check the wiring to on the plug.

Posted on Oct 17, 2013


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Posted on Jan 02, 2017

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SOURCE: code p0401-exhaust gas recirculation flow insufficient detcted

these vehicles as well as every other Ford vehicle has had problems with the DPFE sensors going bad. Ford had a program for this problem but was limited to time and mileage. You can contact a dealer to see if it still qualifies if not the sensor will need replacement. this is very easy to replace

Posted on Nov 24, 2008

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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

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SOURCE: I Have a 1996 Lexus Es300 With Error Code P0401

this not a major problem,its a system that provides a small portion of exhaust gas to intake system to perform power, but no much, try to reset by disconnect the negative battery terminal few minutes

Posted on Apr 18, 2009

  • 3 Answers

SOURCE: code on diagnostics p0401

Code on diagnostics p0401:

What is going on?
Exhaust Gas recirculation low flow detected means that: there is vacuum problem in the EGR system - between the combustion chamber, EGR valve (mechanical - blown up diaphragm or clogged airlets/hoses) , EGR Modulator Valve (mechanical - blown up diaphragm, dirty EG/air filter or clogged airlets/hoses) and Vacuum Switching Valve ((mechanical - blown up diaphragm or clogged airlets/hoses OR electrical - VSV not properly synchronizing with the ECM, for instance).

This causes the combustion chamber temperature to increase and produce Oxides of Nitrate (NOx) that is out of an acceptable emission range. This triggers the Malfunction Light (check engine light) to stay on (after a couple of driving cycles)!
Solution: Focus on EGR airways (hoses...) and organs (EGR valve, EGR Modulator, VSV), clean, check or replace the defected one. VSV seems to be criticale as it plays electrical & mechanical function. Once the repair is done, Clear the P0401 code using an OBII scanner.

Posted on Jun 16, 2009

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SOURCE: SEL code P0401 (2004 Mitsubishi Galant 2.4L)

Check for

vacuum leaks on intake manifold,

the air tube between the air filter.

intake manifold vacuum hose.

clean throttle plate with Berryman carburator cleaner

SEE sample picture HERE

Also remove carbon built up behind the EGR valve and the EGR passage tube.


Vacuum leak WILL offset the intended 14.7 to 1 air fuel ratio.

More un-metered air (leaks) will lean out the fuel mixture.

Use small amount of Berryman carb clearer at potential air leak area will help you identify trouble spot.

At idle,just spray and listen for the RPM surge.

The in-rush of carb clearer will increase the RPM on the motor.

Record the problem spot(s) and address it later.


EGR carbon built up require 2+ hours to clean from start to finish.

You will need a new EGR base gasket before your start.

Locate and remove the EGR valve after the vehicle is cool down.

Carefully record the connector and vacuum line (for older vehicle) location by drawing an easily to follow diagram.

Remove the EGR valve.

Inspect the location of the carbon built-up inside the valve and the EGR passage tube.

SOAK these areas with WD-40 spary.

You will need a small screwdriver,cloth hanger and lot of newspaper and time to get this cleaning done right.

RE-SOAK the carbon and let it sit for over-night will also help.

One the last round,pass a shop vacuum of the EGR valve and the passage pipe.

Install the new EGR gasket and connectors.

Allow the vehicle to warm up outdoor to burn up any remaining WD-40.

Take it for a test drive.

Please rate my answer if it's useful to you.



Posted on Dec 19, 2009

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