Question about Mitsubishi Cars & Trucks

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P0401 code I recently replaced the front catalytic converter and oxygen sensor on my 2001 1.8L Mitsubishi Mirage. A new code popped up after the install, P0401: Insufficient exhaust recirculation. I had an audible exhaust leak at the exhaust manifold/front cataytic converter, but I put in a new gasket and permatex sealant and there is no sound of an exhaust leak. This did not clear the code however. Is it likely that a small inaudible exhaust leak could cause this code? What did I likely do during the install that triggered this code? Any answers or ideas would be appreciated.

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1 Answer

Do you not look up the codes & diagnose them?

Google PO401

Posted on Jan 06, 2013

  • 2 more comments 
  • John B Jan 06, 2013

    I did google it many times, but nothing has been clear concerning whether or not a small exahust leak can cause the code

  • Anonymous Jan 06, 2013

    PO401 is a very common egr code for insufficient exhaust flow detected I don't see how you can't find a couple hundred sites on it to read Most likely a bad egr valve unless the flow to it is restricted

  • John B Jan 06, 2013

    Yes, I have been to about a hundred of those sites. I understand that the code normally involves a bad egr valve and carbon deposits, etc. What I would like to know is if an exhaust leak before the catalytic converter could trigger the code also. I did not have the code before replacing the converter.

  • Anonymous Jan 08, 2013

    The PO401 is an egr code. If you had exhaust leaks before the converter you would have O2 Sensor codes

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Posted on Jan 02, 2017

chuck943
  • 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

badealer888
  • 414 Answers

SOURCE: my 2000 rodeo check engine is on so i hade it

Check the vacuum lines going to egr. An intake cleaning may also help.

Posted on Jun 26, 2009

Mustgo
  • 2359 Answers

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.


Cheers,

Mustgo

Posted on Dec 19, 2009

redbeard00
  • 957 Answers

SOURCE: 2000 isuzu trooper: OBD-II Trouble Code: P0401 Insufficient EGR F

Your SUV is really giving you a hard time, lol. Sorry but I've had those days too.
I would try to check if you have blocked EGR passages. If ok check for restricted MAP sensor vacuum hose/passage or restricted exhaust. I know you replaced the CAT but if the muffler is blocked then there would still be a restriction. Also check the wiring and connection to the MAP sensor.

Posted on Apr 28, 2010

  • 3640 Answers

SOURCE: check engine light on

Diagnostic code produces P0420 catalyst system efficiency below threshold-Bank 1. Probable causes are listed as follows:
1-air leak in exhaust before rear 02 sensor, 3-Fuel system fault,
4-faulty catalytic converter.

Posted on May 31, 2010

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3 Answers

01 odyssey p0401, p0420, p0401 and tcs light on


Hi there:

DTC 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.

Symptoms
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

Possible Solutions:
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)
Replace the EGR valve


DTC P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar.

This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

Symptoms: The main symptom to the driver is the illumination of the MIL (malfunction indicator lamp). You will likely not notice any drivability problems, although there may be symptoms. For example, if the substance inside the catalytic converter is broken or failed, it may be restricting the exhaust which will result in a feeling of reduced power output from the vehicle.

A code P0420 may mean that one or more of the following has happened:
Leaded fuel was used where unleaded was called for
A damaged or failed oxygen sensor (HO2S)
Downstream oxygen sensor (HO2S) wiring damaged or connected improperly
The engine coolant temperature sensor is not working properly
Damaged or leaking exhaust manifold / catalytic converter / muffler / exhaust pipe
******** spark timing
The oxygen sensors in front and behind the converter are reporting too similar of readings
Leaking fuel injector or high fuel pressure
Cylinder misfire
Oil contamination

Possible Solutions: Some suggested steps for troubleshooting a P0420 error code include:
Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
Inspect the downstream heated oxygen sensor (HO2S), replace if necessary
Replace the catalytic converter

Overall probably the biggest mistake vehicles owners make when they have a P0420 code is to simply replace an oxygen sensor (H02S). It is important to do proper diagnosis so you're not wasting money replacing parts unnecessarily.

We strongly recommend that if you need to replace the catalytic converter that you replace it with an OEM unit. Second choice would be a high-quality replacement part. There are many stories in our forums where folks replaced the cat with a cheaper aftermarket one only to have the code return shortly thereafter.

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.


Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Jun 28, 2012 | Honda Odyssey Cars & Trucks

1 Answer

Got code po 421


Hi there,

P0421 = Warm Up Catalyst Efficiency Below Threshold (Bank 1)

This means the HO2 (Oxygen) Sensor downstream of the catalytic converter on bank 1, is detecting that the converter is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

Sep 19, 2011 | 1999 Mitsubishi Mirage

3 Answers

2001 Nissan Sentra. Car starts with no power, but after a few restarts, gain power again. Code is PO420.


Hi, P0420 code means a catalytic converter fault.
The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
  • Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
  • Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
  • Inspect the downstream heated oxygen sensor (HO2), replace if necessary
  • Replace the catalytic converter

Jul 22, 2011 | Nissan Sentra Cars & Trucks

1 Answer

How do you fix a code 420


P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

Symptoms: You will likely not notice any drivability problems, although there may be symptoms.

Causes: A code P0420 may mean that one or more of the following has happened:
* Leaded fuel was used where unleaded was called for
* An oxygen sensor is not reading (functioning) properly
* The engine coolant temperature sensor is not working properly
* Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
* Retarded spark timing
* The oxygen sensors in front and behind the converter are reporting too similar of readings

Possible Solutions: Some suggested steps for troubleshooting a P0420 error code include:
* Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
* Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
* Inspect the downstream heated oxygen sensor (HO2), replace if necessary
* Replace the catalytic converter

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

Hope helps (remember to rate and comment this).

Sep 29, 2010 | 1998 Mitsubishi Eclipse

3 Answers

Po420 code monte carlo ls 2001


PO420 code is for catalyst system efficiency below threshold (bank 1) Usually it means that it is time for a new catalytic converter on bank number 1. Cylinder bank number 1 is always the bank with the number 1 spark plug in it.

Apr 20, 2010 | 2001 Chevrolet Monte Carlo

2 Answers

P0401,P 0420, CODE IN HONDA ODYSEY


P0401- Bad EGR valve
P0420- Most likely cause is a bad O2 sensor(s) at the catalytic converter

Sep 08, 2009 | 2001 Honda Accord

1 Answer

PO420


Not just a faulty catalytic converter will trigger this code. Many other issues can trigger this code.

  • Leaded fuel was used where unleaded was called for
  • An oxygen sensor is not reading (functioning) properly
  • The engine coolant temperature sensor is not working properly
  • Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
  • Delayed spark timing
  • The oxygen sensors in front and behind the converter are reporting too similar of readings
Possible solutions:
  • Check for exhaust leaks at the manifold, pipes, catalytic converter.
  • Replace Coolant Temperature Sensor
  • Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
  • Inspect the downstream heated oxygen sensor (HO2)
  • Replace the catalytic converter
  • Have timing adjusted


Aug 25, 2009 | 2002 Toyota Camry

2 Answers

2002 Mitsubishi Galant Front Catalytic Converter


A muffler shop should be able to replace just the converter

Aug 07, 2009 | 2002 Mitsubishi Galant

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