Toyota Repair/po401


QUESTION: does po401 damage my engine what will it to my car

ANSWER: No, it will not cause damage to the engine, it is for a malfunction of the exhaust gas recirculation (EGR) system, it is and emission control device and has no affect on drivability.

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QUESTION: so what will it actually do what will be the side effects, if it does not damage the engine and its just a exaust problem what can I expect long term if not corrected. Im confused what is the purpose if egr and what will po401 do then.

Hello, the purpose of the EGR system is to recirculate some of the exhaust gases back into the intake system and into the combustion chamber, this causes lower combustion temperatures which in turn reduces nOX (oxides of nitrogen) emissions which is a known greenhouse gas, this type of system was introduced at around 1970 due to the federal clean air act legislation. The 401 code simply means that there is not enough exhaust gas being recirculated either due to a defective EGR valve, modulator valve, disconnected vacuum hoses, clogged passage between the valve and the intake system or a bad vacuum switching valve that controls the system. If you live in a location that has annual or by annual emission testing it will fail the test and the problem has to be fixed before registration renewal.

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Ted Ritter


I have more than 28 years experience as toyota technician, I will be able to answer most questions related to the Toyota product line up to the present year models,I am located in the US but welcome questions from other regions of the world. When asking a question please provide specific information: year,model, engine,transmission information. Provide as much information as possible including a brief repair history if possible. I have been a volunteer here for more ten years an have answered over 16,000 questions helping Toyota owners with their problems and save thousands of dollars without any compensation, some of my answers are published on many other websites including google and various automotive forums. DONATIONS ARE VERY MUCH APPRECIATED, IF YOU HAVE RECIEVED HELPFUL INFORMATION PLEASE MAKE A DONATION. AS OF TODAY (JULY 22, 2014) ALL REQUESTED GRAPHICS, ILLUSTRATIONS, DIAGRAMS, PHOTOS, WILL REQUIRE THE MINUMUM DONATION UP FRONT.


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