P0420 Cat Efficiency diagnosing
08-19-2017
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P0420 Cat Efficiency diagnosing
I've been putting off this code for some time and I'm finally dealing with it. I think a while back I replaced the O2 sensor (i think it was the 02 and not the AF) I went to Oreilly's and used their scanner to look at the live data and here is what I got at about 2800 rpm:
Does this look off to anyone? Enough to condemn the cat?
Does this look off to anyone? Enough to condemn the cat?
08-19-2017
#2
If you think a good mechanic is expensive, try hiring a bad one
Re: P0420 Cat Efficiency diagnosing
I think a while back I replaced the O2 sensor (i think it was the 02 and not the AF)
Was this replaced in attempt to deal with the P0420 code, or was it for some other reason?
If the PCM (ECM) decided to fail the cat, it probably needs a cat.
Things to consider:
High mileage
contamination/poisoning/oil consumption
misfires/poor running/ loss of fuel control
exhaust leakage
skewed sensors
Last edited by ezone; 08-19-2017 at 12:08 PM.
08-19-2017
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I would bet it was the O2 sensor. I wouldn't have done the A/F sensor I dont think. I replaced it thinking it might clear the p0420. And if I remember right, it did but not for too long, came back on.
It's a 2003 civic Si hatch with 162k on it. I haven't noticed any misfires.
Does the live data tell you anything? Seems like it's reading rich, right?
It's a 2003 civic Si hatch with 162k on it. I haven't noticed any misfires.
Does the live data tell you anything? Seems like it's reading rich, right?
08-19-2017
#4
If you think a good mechanic is expensive, try hiring a bad one
Re: P0420 Cat Efficiency diagnosing
O2 is the rear sensor. AF is the front sensor.
No you don't have enough scanner data to make any sort of conclusion....and you can't outguess the ECM. (I did notice the rear sensor swings but I don't know enough about the conditions to make any guess)
Same for deciding if it's rich, there is no data showing in the video to indicate one way or the other.
We DO know the ECM already judged it as bad.
You just have to figure out if it is real and natural (mileage says this is pretty darn likely),
induced and needs something corrected so the next unit doesn't die prematurely (contaminated/poor running/tune),
or completely false for some reason (like effed up AF/O2 sensors or exhaust leaks).
If you're in Cali make sure you put a genuine Honda cat or a CARB certified cat on it. Even if you aren't in Cali, I'd put a CARB certified cat on it. Probably will have the best warranty as well.
49 state/Federal and cheaper cats may not last long enough to be worthwhile. Many can't keep the computer happy at all.
No you don't have enough scanner data to make any sort of conclusion....and you can't outguess the ECM. (I did notice the rear sensor swings but I don't know enough about the conditions to make any guess)
Same for deciding if it's rich, there is no data showing in the video to indicate one way or the other.
We DO know the ECM already judged it as bad.
You just have to figure out if it is real and natural (mileage says this is pretty darn likely),
induced and needs something corrected so the next unit doesn't die prematurely (contaminated/poor running/tune),
or completely false for some reason (like effed up AF/O2 sensors or exhaust leaks).
If you're in Cali make sure you put a genuine Honda cat or a CARB certified cat on it. Even if you aren't in Cali, I'd put a CARB certified cat on it. Probably will have the best warranty as well.
49 state/Federal and cheaper cats may not last long enough to be worthwhile. Many can't keep the computer happy at all.
08-26-2017
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Are those fancy converter bolts necessary (seen here: ) to connect the outlet of the converter to the pipe, or would regular bolts do the same thing? Those bolts are crazy expensive!!
08-26-2017
#6
If you think a good mechanic is expensive, try hiring a bad one
Re: P0420 Cat Efficiency diagnosing
Those splined bolts come already installed in a genuine Honda converter.
If you are going to use an aftermarket converter, I'd be using whatever nuts and bolts I have that will fit.
If you are going to use an aftermarket converter, I'd be using whatever nuts and bolts I have that will fit.
08-26-2017
#8
If you think a good mechanic is expensive, try hiring a bad one
Re: P0420 Cat Efficiency diagnosing
The correct m10x1.25 exhaust nuts are a locking type. No lock washers. The nuts have a wide base that takes the place of a washer.
You might want some anyway....
My personal preference is no lock washers and no threadlock of any kind.....If you use decent quality hardware and get them tight enough, they don't normally back off on their own. In the rust belt they might never come apart with a wrench later on anyway.
You might want some anyway....
My personal preference is no lock washers and no threadlock of any kind.....If you use decent quality hardware and get them tight enough, they don't normally back off on their own. In the rust belt they might never come apart with a wrench later on anyway.
