2007 Accord - P0420 Code

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Thanks all, I'll reset the light add fuel additive and do an italian tune up and then see what happens.
 
Interesting non-fouler spark plug mount solution. It can fool the engine computer (OBDII) algorithms by getting the rear O2 sensor out of most of the exhaust flow, essentially flat-lining the signal which looks like a functioning cat. Of course the car will pollute more. Wondering if state emissions test station personnel now use a mirror to look for O2 sensor tampering these days?
And of course, with a bad cat, the car can fail CO and HC emissions levels in the test station measurements.

Anybody have the CataClean thing work for them? I'm seeing little possible benefit since the contents are burned in the combustion chamber before getting to the cat, for the most part anyway. Could be enough gets through duing open-loop operation (during a minute or 2 after cold starts) or during brief rich operation.
 
The anti-fouler works because it gets the downstream O2 sensor out of the airstream and it no longer measures the O2 content exiting the cat effectively.

If the downstream sensor is not responsive, slow or dirty or whatever, it's probably not going cause a CEL but rather, will fail to recognize a failing cat.

Replacing sensors is not going to get rid of a P0420. (Not for long, at least).
 
Curious if I can test using this procedure for both upstream and downstream using Ohm readings? Does anyone know the range?
 
That P0141 is for the heater circuit only on the O2 sensor. A resistance (units of ohms) reading simply looks for a thinning or broken heater wire, like when a bread slice toaster wire breaks or thins, or a light bulb filament breaks, you would get very high reistance when the circuit is broken (open or a thinned wire).

Somebody above advised going ahead and replacing the O2 sensors in an older engine like that. Its true these things gradually build up a layer of carbon and varnish on them which gradually degrades performance.
Probably good to change 02 sensors every 10 years or 150,000 miles regardless of no check engine light.
 
Did a reset on the light, added berryman B12 and Italian tune up, so far light hasn't come back. Fingers crossed, will report back.

Thanks all.Â
 
Originally Posted by maverickfhs
Did a reset on the light, added berryman B12 and Italian tune up, so far light hasn't come back. Fingers crossed, will report back.

Thanks all.Â


Depending on when your car runs the 420/430 test - the light could come on in 50 miles or over 500. It will come back on, I seriously recommend the spark plug anti-fouler trick if the light does come back on. The P0420/0430 codes are calibrated to come in when the threshold of the cat efficiency drops 10%, that's not much at all.
 
Last edited:
Originally Posted by GMBoy
Originally Posted by maverickfhs
Did a reset on the light, added berryman B12 and Italian tune up, so far light hasn't come back. Fingers crossed, will report back.

Thanks all.Â


Depending on when your car runs the 420/430 test - the light could come on in 50 miles or over 500. It will come back on, I seriously recommend the spark plug anti-fouler trick if the light does come back on. The P0420/0430 codes are calibrated to come in when the threshold of the cat efficiency drops 10%, that's not much at all.


Is it similar to this one?
 
Originally Posted by maverickfhs
Originally Posted by GMBoy
Originally Posted by maverickfhs
Did a reset on the light, added berryman B12 and Italian tune up, so far light hasn't come back. Fingers crossed, will report back.

Thanks all.Â


Depending on when your car runs the 420/430 test - the light could come on in 50 miles or over 500. It will come back on, I seriously recommend the spark plug anti-fouler trick if the light does come back on. The P0420/0430 codes are calibrated to come in when the threshold of the cat efficiency drops 10%, that's not much at all.


Is it similar to this one?



Yes, those are the ones I use. You can also buy special made ones that won't require drilling out for more money if you rather do it w/o drilling.
 
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The spark plug non foulers work great if you can get away with it, The P0420 is the code that always seems to show back up right after you fix it.

IMG_0179.jpeg
 
That cartoon is hillarious!!! But seriously, I've only had 1 420/430 come back after a non-fouler treatment and that particular car was burning a lot of oil. The fix lasted about a year. I've done about 25-30 of these over the years so that's a pretty good chance of odds it will work.
 
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