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P0420 CEL Code?

Discussion in '1st Gen. Tacomas (1995-2004)' started by dietcookie, Dec 21, 2010.

  1. Dec 21, 2010 at 1:09 AM
    #1
    dietcookie

    dietcookie [OP] New Member

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    I've noticed I get a P0420 CEL code whenever I head out to higher elevations, weather it be on the road or on the trail. I've gotten it a couple times and usually just clear the code only to have it come back again. Seems like the normal procedure to diagnose it is to

    1) Check for exhaust Leaks
    2) Replace Front/Rear O2 sensors (the front was replaced recently already but I got a specific CEL code that time..)
    3) Replace the Cat.

    I have a 2000 Tacoma 4x4 3RZ-FE with 264,000 miles on it. I figure by this time the O2 sensors should be shot and probably the cat too but I'd rather fix what is wrong. With this type of mileage, should I just replace the rear O2 sensor anyways, clear the CEL and if that doesn't work, replace the cat? Thanks.
     
  2. Dec 21, 2010 at 4:45 PM
    #2
    shitroc

    shitroc Master of War

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    Ant
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    that would probably be your best bet,try the easier cheaper fixes first before having to spend some big bucks.
     
  3. Dec 28, 2010 at 10:31 AM
    #3
    el contrador

    el contrador Member

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    André
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    Check for Exhaust leak first, specialy close to O2 sensors... I had a very small leak on the second flange of # 2 cat and it triggered the p0420 code... fixed it and light came off!!

    If you have a very small leak and you are running at a constant speed, it will pull air from the hole instread and fresh air will mess up the o2 sensor reading!!
     
  4. Jan 4, 2011 at 9:22 AM
    #4
    YotaDude01

    YotaDude01 Kentucky Boy

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    I just got that same code on my 01'. The guy at autozone same it could be all the things that you all have already said. But also he said this weekend that he has had alot of cars come in with that same code. He said bad gas can cause it to. I turned off the light after refueling with a better brand of fuel and the light hasnt come back on. But its only been a day. So i guess ill see if it really was the gas.
     
  5. Jan 4, 2011 at 12:58 PM
    #5
    el contrador

    el contrador Member

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    Original a to z
    It's possible, the P0420 code can light up if you are using gas that as more then 12% ethanol in or as less then 85 octane...

    Also, you might wanna check for small exhaust leaks close to the second O2 sensor. I've resolved my problem by changing the gasket between the second cat and the extention pipe, the one right before the second O2 sensor. When you are driving at a constent speed, the flow can create a vacuum and pull fresh air from outside and will fals the reading of the sensor opening the check engine light.

    So before anything, check for exhaust leaks by blocking the exhaust and check where air is coming out... specialy very small one neer the sensors!!

    Let me know if it resolved your problem.
     
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