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Toyota Repair/2000 Camry check engine code P0420


QUESTION: Hi--thanks so much for offering your experience and expertise.
We bought the car used a year and a half ago -- 4 cylinder engine with 75K miles on it. Check engine light went on soon after we bought it--mechanic replaced VSV solenoid and EGR position sensor, repaired exhaust flex, cleaned out exhaust ports and the light went off for over a year after that.

It came on again a couple of weeks ago with P0420.  Mechanic said it could be the o2 sensor or catalytic converter.  He replaced the rear sensor -- but the check engine light came back on the next day.  Now he wants to replace the cat.

My questions, after a little internet research:

1.  People report that this P0420 code may go on because of leaks in exhaust system,fuel filler pipe, gas tank,fuel lines or even a loose cas cap.  Should I instruct mechanic to do a thorough check of above first?

2.  The mechanic did not use a Toyota brand o2 sensor.  Would this make a difference in terms of light going on again?  If we replace the cat, is a Toyota brand cat required -- as some say -- in order to keep the check engine light off?

3. Some people say -- with this code -- to do fuel injection treatment, clean PCV valve, check for loose,cracked or clogged vaccuum hoses.  Any merit to these ideas?

4. Do 2000 Camrys tend to have these engine problems?
Thank you in advance for your advice on these questions.

ANSWER: This code is specific to a catalityc converter failure, O2 sensor fault codes are different, yes these camrys are known to have cat converter problems.

---------- FOLLOW-UP ----------

QUESTION: Thanks for your response.
*Do we need to use Toyota brand replacement converter? (or just have replacement welded in by muffler repairman?)
*Was it a problem that new sensor was not Toyota brand?
*What causes these cat problems?  Should anything else be checked/changed --as in questions 1 and 3 above?

ANSWER: I always recommend toyota oem parts but they are very expensive so a good substitute will most likely be ok, the muffler shop option is one, stay away from the very cheap converters and O2 sensors, make sure the give you some sort of warranty on the new converter.

---------- FOLLOW-UP ----------

QUESTION: Thanks so much for your time and advice. (I hope to do the rating thing later today).  If you don't mind, please let me know -- before I go -- whether or not I should be checking or changing anything else that might be causing problems with this code?  As I wrote above, I have read advice like:  Check for leaks in exhaust system,fuel filler pipe, gas tank,fuel lines or even a loose cas cap.  Check fuel injector, clean with fuel injection cleaner.  Check and clean PCV valve.  What do you think?

"Check for leaks in exhaust system,fuel filler pipe, gas tank,fuel lines or even a loose cas cap.  Check fuel injector, clean with fuel injection cleaner.  Check and clean PCV valve.  What do you think?"
The only thing that should be checked is for an exhaust leak since this can cause a converter to overheat, the others are not related and do not cause this code, in my experience I have never seen one of them cause a cat converter to fail, they fail basically because they overheat or just due to age, overheating can be caused by an engine misfire, lean air/fuel mixture, exhaust manifold leaks.The mechanic should check and make sure none of those conditions apply before replacing the converter.

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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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