Question about 1995 Lexus ES 300

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Diagnostic code "P0401". I have already replaced the EGR and had a mechanic diagnose it saying that it needs "EGR VAC S/W VALVE BACK PSI" and "TRANSDUCER". He quoted me $486.75 to do the repair. He claimed that the parts could only be purchased at the dealership and the parts were around $400. I visited the dealership and they guessed at what they meant and quoted me $200 for the parts. Can anybody give me a straightforward answer as to what I need to replace? Thank YOU!

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The EGR can be checked by putting vacuum on the line while the engine is running. The easiest way if you don't have a vacuum pump is to take the hose off and **** on the fitting with your mouth. (I agree that it's not really sanitary but sometimes you do what is needed) You may be able to borrow a hand vacuum pump from a parts store for a small fee. If the engine stumbles or runs rough when you pull vacuum, the EGR valve is bad. The next thing would be to check the EGR modulator. It is located right next to the EGR and has 3 hoses coming off it. You need to remove the modulator and put vacuum to the port on the bottom. Same process as the EGR. If it holds vacuum, it is good. If not, replace it. The modulator should be less than $100. If they can't find it for your car, a Camry SE V6 for the same year will fit.

Posted on Sep 28, 2010

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This code is usually caused by blockage and can often be cleared just by cleaning out the passages. Unfortunately I cannot find the procedures for you car. If you want to try cleaning, perhaps you can get a repair manual. The code can also be caused by the EGR valve or solenoid, but these can be tested for proper operation. Did they test them? Which part did you already replace? I don't know why they quoted the sensor, as the sensor is giving a reading, albeit a low flow reading. There is an aftermaket valve for $175, but I could not find a price on the vac solenoid.

Posted on Sep 28, 2010

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It shows code P0401. Already replaced the EGR valve and catalytic converter plus sensors. What now.


You didn't say if you have any symptoms so I will assume you don't. After you made the repairs, you have to have the code removed. Any major auto parts store will do it for free. If the code don't come back, its fixed.

Mar 23, 2015 | 2001 Hyundai Santa Fe

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Why does my 2002 Acura Rl have a error code of P0401


P0420-catatytic convertor failure Replace convertor
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Jun 01, 2014 | 2002 Acura RL 3.5

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Egr fault code p0401


Hi there:

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


Hope this helps.

Dec 06, 2012 | Cars & Trucks

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Obd2 codes p0401 and p1744


P1744 -transmission intermittent/torque converter is a manufactures code;they have that problem,like the wipers coming on.
P0401-egr valve flow insufficient;replace or remove,spray B-12 on and around all openings;clean let dry new gasket.

Jun 28, 2012 | 1999 Mercury Sable

2 Answers

Fault code p0401


This error means Exhaust Gas Recirculation Flow Insufficient Detected.

You can deatils on the following site http://www.permoveo.ltd.uk/tabid/122/OBD-Error-Code/P0401/Diagnostics/Hyundai/Default.aspx

but for convenience I have reproduced that information here:
.
Generic OBD Error Code Details for P0401 Exhaust Gas Recirculation Flow Insufficient Detected What does this mean? OBD Code P0401refers to
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. SymptomsPossible sumptoms of OBD code P0401
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. CausesPossible causes of OBD code P0401
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 SolutionsIn 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 Related CodesP0400 P0402 P0403

Jul 12, 2011 | Hyundai Tucson Cars & Trucks

2 Answers

1999 mercury sable engine code p1744,p0401. Failed e check. EGR looks new, replaced egr solenoid then cleared codes. what more can i do about the p0401 code and the p1744 code Thanks


for p0401:
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.

Jul 08, 2011 | 1999 Mercury Sable

2 Answers

Check light on,problem shows on p 0401


P0401-Insufficient flow in the exhaust gas recirculation system (EGR-valve). Check your gas cap for cracked seal, check EGR valve (make sure all vacuum hoses aren't leaking), check also VSV (vacuum switching valve) for proper operation. Its best to get an owner's manual or an experienced mechanic to diagnose!!hopefully this helpd

Oct 06, 2010 | 1998 Toyota Camry

3 Answers

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).

Effects?
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.

Dec 21, 2008 | 1996 Lexus LX 450

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