CEL Code= P0420...any ideas?

Lincoln LS

  1. BrianDye

    BrianDye Dedicated LVC Member

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    Went to AutoZone, got my code read, came out with

    P0420
    Catalyst Efficiency Low-Bank 1

    Explination:
    The oxygen sensors monitor the Catalytic Converters ability to store oxygen

    Probable Cause:
    1. Catalytic converter defective (Failure possibly due to #2, 3, or 4)
    2. Engine misfire or running condition
    3. Large vacuum leak
    4. Engine oil leaking into exhaust valve guide (reciept's ripped here) ..rings


    (They printed it off for me, and the reciepts ripped after guide, but theres like 2 words before "rings")



    I dont get it, are my cat's bad? Or do I have a large vacuum leak? Or is my oil leaking into the exahust...?

    How can I narrow this down and fix it?

    2000 LS V8, with 174,000 miles.
     
  2. Lincoln Jealous

    Lincoln Jealous Dedicated LVC Member

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    either your cat is bad at 174k, or its just a o2 sensor
     
  3. joegr

    joegr Dedicated LVC Member

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    Is your car running okay?
    Is your oil consumption less than 1 qt for 5000 miles?

    If the above answers are both "yes", then you can rule out most of that stuff.

    Your mileage is such that the Catalytic converter(s) could be worn out. It is also high enough that your O2 sensors could be bad. If you're going to try the guessing method at fixing this, then the O2 sensors are the cheaper things to try first. Start with the post cat sensor, and if that doesn't do it, try the pre-cat. If either does fix it, you may want to replace all four at this point.
     
  4. BrianDye

    BrianDye Dedicated LVC Member

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    Eh, I cant say about the oil, weve only had it for about 600 miles so far, yea it runs perfectly and very smooth, ive checked the oil a few times, and it seems pretty much the same every time, and it doesnt drip or leak anything.

    How hard are the 02 sensors to change? How much are they a piece, if im gonna do one, I might as well do all 4 while im at it.
     
  5. Lincoln Jealous

    Lincoln Jealous Dedicated LVC Member

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    +1

    most likely its the post cat sensor, sensors are about 45 bucks each, you can get them at the auto store

    very simple to change, takes about 3 minutes per sensor, start the car to warm up the exhaust for about 2 minutes first, makes it easier
     
  6. DrewSG

    DrewSG Active LVC Member

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    My CEL on is on for the same code, car runs and drives perfectly fine as well
     
  7. BrianDye

    BrianDye Dedicated LVC Member

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    Yea man I'm just a very anal person lmfao I can't be cruising with a CEL on haha.
     
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    • craigh

      craigh Well-Known LVC Member

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      Poor mans diagnosis - switch the O2 sensors from side to side. Will take about 10 minutes. See if it throws the same code. If the same, it is not the O2 sensors and you can look at the cat or other symptoms. If the O2 sensors are bad, it will throw a P0430, which is a lean condition on bank 2. If it throws a P0430, then just switch either the front or back sensor and see if the code stays the same or changes, you can then narrow down which O2 sensor it is, front or rear.

      The O2 sensors just take a minute to change out. Very simple, just remember to put some anti seize on them when putting them in. Good luck.
       
    • BrianDye

      BrianDye Dedicated LVC Member

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      Craig-that would be alot of trips to Autozone LOL I think they'd hate me after the first few lol, I'll have to wait and try that when we get some warmer weather and find a writeup on how todo it
       
    • exceptionaLS

      exceptionaLS Dedicated LVC Member

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      Hey Brian. This code was on my car, and I sold the car with it on. I went ahead and bought 2 catalytic converters though when I thought I could fix it, before I decided to pull the trigger on buying a new car, I also had a terrible overheating problem so it wasn't only the p0420 code that made me sell it. I think that checking the o2 sensors (maybe just buy 2 and swap them on each side just to check if they work then buy more if you need them) is a better plan than buying anything major. I had driven with cylinder misfires (not sure which ones exactly) for at least 3000 miles over the course of owning the car, that's why I thought that I should just buy new catalytic converters (just thinking I destroyed them by driving with the misfires) but I guess that I should have listened to advice I got on this forum about buying the cheap stuff first and then if that doesn't work to buy the more serious parts. Just my 2 cents, I bet if you search through old posts using the search function you can find my jarbled attempt to get the code fixed atleast and probablly more useful information. Good luck man. Props for getting the thing fixed right.
       
    • craigh

      craigh Well-Known LVC Member

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      Around here, O'Reilly also has scan tools that you can use.
       
    • pektel

      pektel Dedicated LVC Member

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      exactly. pay the deposit, then you get the deposit back when you return the tool.
       
    • BrianDye

      BrianDye Dedicated LVC Member

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      God what would I do without you guys haha I never thought of that, AND my AutoZone has the biggest window decal ever advertising that they rent out tools lol
       
    • Lincoln Jealous

      Lincoln Jealous Dedicated LVC Member

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      o2 sensors is a 5 minutes job, i bet that its the sensor, driver side, past the cat. replace that and uplug the battery for 1 minute and restart the car, if the light doesnt come back the job is done, if the CEL comes back now you have a "good" sensor you can switch with the other ones
       
    • BrianDye

      BrianDye Dedicated LVC Member

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      Sweet, do you happen to know of any write ups or anything?
      I have no friggin clue where the hell it even is, I know on 2nd gen explorers you gotta remove the center console to get at it
       
    • joegr

      joegr Dedicated LVC Member

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      Put the front of the car up on ramps and crawl under it. You can't miss them. Look for for the blue and the green connectors.
       
    • BrianDye

      BrianDye Dedicated LVC Member

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      an LS on ramps!?!? Mine sits so low it would scrape the rear bumper to hell!
       
    • JennsLincolnLS

      JennsLincolnLS LVC Member

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      An LS on One ramp is bad enough! And the bumper does scrape so i would advise against ramps but a floor jack would probably work better! I had to use a board to graduate mine onto a ramp! I am having the same problem with my LS and I just replaced all 4 o2 sensors the code was p0430 when I started the car after disconnecting the battery and replacing the 4 o2 sensors (I used bosch from O'reilly's) the code was gone 2 days later I am getting this code p0420 I think that by driving my car for 2 months knowing the o2 sensors needed done ruined my cats! I would be careful driving it until you figure out what it is that is wrong. And I had to have help breaking my sensors loose but you're a guy you should have no problem and btw a crecent wrench works just as well ( a really big heavy one) cuz I couldn't get the tool into the lower o2 sensor it was so close to the tranny pan? (I'm still learning my car so I'm not sure what they were close to just that I couldn't get the tool that fit in that space!
      Good Luck!!
      Jenn
       
    • JennsLincolnLS

      JennsLincolnLS LVC Member

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      Ok so I just realized that the original post for this was 2009 don't mind me I'm a novice at this!!!!!!!!
      Jenn
       

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