Again with the CEL! (P0421)

BoldlyGoing

BoldlyGoing

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So, right on schedule (just before I have to go in for emissions testing every year) popping P0421 this time which is a new one on me.

So now we play the maybe it’s a Cat, maybe it’s a plug, maybe an O2 sensor game. Pulled the battery cable yesterday to see if it would come back, sure enough, it popped again today.


Any tips to tracking this down? I have a spare new Bank 1 O2 sensor, so I figure I’ll try that first.

Can you even buy just a mini-cat? Have I mentioned I hate this nonsense emission BS?

No symptoms while driving.
 
Emissions suck and worthless really. I know those sensors are expensive but if you can I’d pop ‘em both in. I am no mechanic but it seems to me the cat will bust apart to cause an issue and you will hear the rattle or smell the burning. Hopefully someone will chime in and confirm or call me a liar before you change the sensors for nothing.
 
dangjalopy said:
Emissions suck and worthless really. I know those sensors are expensive but if you can I’d pop ‘em both in. I am no mechanic but it seems to me the cat will bust apart to cause an issue and you will hear the rattle or smell the burning. Hopefully someone will chime in and confirm or call me a liar before you change the sensors for nothing.
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Worthless yes, except that I can’t renew my registration without passsing.

Here’s hoping the O2 sensors do the trick. Really not wanting to drop $300 on new cats.
 
Don't you wish you lived where I live? No emissions, no inspections... nothing.

Now you'll understand why I'm gutting ALL of my emissions and disabling the systems via the PCM.

You have NGK sensors, right?

If so, it very well could be your cats. Those pre-cats seem to start getting iffy around 100k miles. You can't just buy one pre-cat to my knowledge, but a full replacement pre-cat downpipe is only around $300.
 
Chris said:
Now you'll understand why I'm gutting ALL of my emissions and disabling the systems via the PCM.
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Not to derail this thread, but what’s the benefit to this? I live in AZ and we don’t do emissions here either thank God
 
Chris said:
Don't you wish you lived where I live? No emissions, no inspections... nothing.

Now you'll understand why I'm gutting ALL of my emissions and disabling the systems via the PCM.

You have NGK sensors, right?

If so, it very well could be your cats. Those pre-cats seem to start getting iffy around 100k miles. You can't just buy one pre-cat to my knowledge, but a full replacement pre-cat downpipe is only around $300.
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It’s such a silly thing. Every year it comes down to some small thing I need to do - last year it was a loos bolt on the flange connecting the cats to the manifold causing a code.

This year, who knows.

As for wishing I loved where you do, if I recall correctly, that’s Oregon or one of those other frozen northern wastelands I ran away from when I got out of high school!
 
Jamison C said:
Not to derail this thread, but what’s the benefit to this? I live in AZ and we don’t do emissions here either thank God
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No benefits other than I can get rid of a bunch of crap I don't need and not have to worry about it breaking or throwing CELs for those common failures.

BoldlyGoing said:
It’s such a silly thing. Every year it comes down to some small thing I need to do - last year it was a loos bolt on the flange connecting the cats to the manifold causing a code.

This year, who knows.

As for wishing I loved where you do, if I recall correctly, that’s Oregon or one of those other frozen northern wastelands I ran away from when I got out of high school!
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Naa, Oregon doesn't freeze at all. Maybe somewhere else, but not Oregon.
 
Chris said:
No benefits other than I can get rid of a bunch of crap I don't need and not have to worry about it breaking or throwing CELs for those common failures.



Naa, Oregon doesn't freeze at all. Maybe somewhere else, but not Oregon.
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No emissions here in Eagle county colorado. However, we freeze often and already have 4ft of snow.
 
MaloStapalo said:
No emissions here in Eagle county colorado. However, we freeze often and already have 4ft of snow.
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Yeah, but it's Colorado... so totally worth it! I'd rather deal with that than the nasty humidity in the south... just my opinion of course.
 
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Chris said:
Yeah, but it's Colorado... so totally worth it! I'd rather deal with that than the nasty humidity in the south... just my opinion of course.
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MaloStapalo said:
I concur. I moved to colorado from North Carolina.
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Yeah, yeah... I’ll take the humidity over the fact that after a weekend in Denver, I felt like the desiccated cicada shells you find all over Atlanta every couple years.


Back to topic, driving home yesterday I finally got some symptoms- Jeep starts running terribly and making little power. Pulled off the shoulder, rotten egg exhaust smell. Throwing multiple misfire codes.



So went ahead and ordered new cats and a new muffler (went with a Flowmaster. I have all of next week off, so seems like I have my work cut out.
 
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Jerry Bransford said:
Not for long, the exhaust gases will blow the pieces that were clogging it that you knocked loose right back into the elements and it will clog up again.
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Yeah- I know.

Brown Santa will bring the new cats middle of next week.


Tempted to just punch it out until the new ones arrive. But I also don’t like tickets... decisions decisions.


Sent from my iPhone using Tapatalk
 
Jerry Bransford said:
Not for long, the exhaust gases will blow the pieces that were clogging it that you knocked loose right back into the elements and it will clog up again.
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Jerry- in your (seemingly infinite) experience, how often are the pre-cats an issue?

I ask because Amazon has updated my estimated delivery date to 12/21. That was for a complete system with pre and main cat.

However, I could go down the road to summit and pick up a dozen different cat’s right now.

Thoughts?
 
So, finally received the new cats. Apparently Ace Ventura delivered them. Holes all over the box. But, no apparent damage.

Wrestled the old ones off this evening (with liberal application of liquid wrench, breaker bar, and a sawzall) - Bank 1 mini cat was completely burned out. Bank 2 looks a little clogged, but not completely shot.

I haven’t been able to look at the main cat - by the time I got it off, it was dark.

So, now time for a beer and a break. I’ll bolt everything back up in the morning.
 
In my research and experience, our little pre-cats seem to be good for 100k or so, give or take. Right at the EPA mandated limit, LOL. Running higher octane fuel (without a turbo or /sc with tune) or oil additives with high levels of ZDDP can shorten their life.
 
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