OBD P0420 Code on Honda CRV 2002

Discussion in 'Honda' started by PookieSoup, Oct 11, 2008.

  1. PookieSoup

    PookieSoup Well-Known Member

    Heya Forumites,

    There's been weird happenings with my beloved CRV. It's a 2002, automatic, 2.4, with close to 190,000 miles. A few weeks ago, I was suddenly getting a boost in MPG on the highway, but not on city driving. In a few instance, my city driving mpg went down 4-6 mpg even though I drove the same route the same way. The highway driving is the oddest. I'm not getting anywhere close to mid-30's mpg by DWL around 45-50 mph, but I'm getting low 30's mpg by DWL at 70 mph. Strange, and I don't know if it has anything to do with my OBD code, which is the the main reason for this post.

    I checked my code, and it was P0420 which is the catalytic converter. It's been going on and off periodically since yesterday. The same code came up about 5 years ago, and I had the catalytic converter replaced. I've been reading up on some other forums and some people 1. don't do anything about it because it doesn't really mean anything 2. check and replace O2 sensors or 3. replace the catalytic converter.

    Can anyone shed some light on this code? I think the catalytic converter is still under warranty, but if it isn't a serious issues, I don't want to go to the trouble to replace it. Could the code be set off by something else other than the converter?

    Thanks in Advance.


    P.S. I'm not that much of a mechanic. I understanding of these parts is limited.
  2. Chuck

    Chuck just the messenger

    This is the catalytic converter, or in my case possibly the ECU's software thinking the catalytic converter has a problem.

    I'd check any recalls on the CRV just in case it's a software problem.

    Daily at Mile 3 I clear it with ScanGage.
  3. mtbiker278

    mtbiker278 Biotech Researcher

    That's a code for a bad catalytic converter. Check you manual to see what the individual warranties are on the specific parts. My 2006 civic threw a P0420 code not too long ago. The warranty for the catalytic converter was 8 years, in which case you would be covered.

    The shop should, but might not, test your oxygen sensors to ensure they are reading properly. However, if they weren't the ECU should throw a code stating that the sensors are malfunctioning and not the Cat.

    It took about a day to get a new cat in from the warehouse and about 3 hours for them to replace it along with a bunch of other things. If your cat is under the CR-V it should take less time.
  4. PookieSoup

    PookieSoup Well-Known Member

    What's the consequences for not replacing it? I just called the shop, and they said I had it replaced in Feb. 2005. Seems kind of quick to be going out again.

    Also, it goes on and off. Not blinking, but maybe the light will come on for 200 miles, then off for 50, then on for 25, then off for 200.
  5. mtbiker278

    mtbiker278 Biotech Researcher

    hmmm... Well it sounds like it might be a faulty sensor. Your ECU determines the effectiveness of the Catalytic converter based on the difference between your 02 readings.

    For example if your upstream (before the cat) read 10 and the downstream (after cat) read 1 your effectiveness would be 90%. Now most ECU have it hardcoded in them a threshold of 95% effectiveness before it'll throw a code. Because your code bounces on and off I would suspect a maginally faulty 02 sensor. I marginally because it's still working to whatever degree the ECU needs, but it's not reading accurately. Have your shop test the electrical outputs of the 02 sensors to see if they are reading properly.

    Generally any car built after year 2000 should go 100k miles before the 02 sensors need to be replaced. The Catalytic converter "should" last the lifetime of the vehicle as well, but that depends on a myriad of variables including fuel quality, engine wear, fuel additives, oil additives, and shock from accidents/rocks.

    worst case scenario is you have a cracked block or leaking head gasket and coolant is leaking into your combustion chamber. This would foul the catalytic converter readily. It's hard to diagnose with this little bit of info.

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