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Discussion Starter #1 (Edited)
Headers and/or Cats: Catalytic Inefficiency solved


WHO: People who upgraded to aftermarket headers without installing any catalytic converter will get a catalytic inefficiency error code. Likewise, people who install high-flow catalytic converter will get the same ***8220;inefficiency***8221; error codes.

WHAT: Catalytic Inefficiency codes on the post cat 0xygen sensor: P0420 (cylinder 1-3) P0422 (cylinder 4-6).
Ref: http://www.obd-codes.com/trouble_codes/generic/p0420-catalyst-efficiency-below-threshold-bank-1.php

WHY: The reason why your OBD-II diagnostic systems report this error code is because the 02 sensors detect an above normal exhaust reading when compare to OEM catalytic converter. The OEM catalytic converter does an excellent job at filtering/cleaning/converting exhaust fumes into cleaner air. The DME/ECU calibrates its post-cat sensors to the OEM catalytic converter performance and specs. Therefore, aftermarket cats do not clean well enough to satisfy the catalytic efficiency monitoring of the DME. This is a very common problem with aftermarket cats especially the high-flow ones.
An ***8220;inefficiency***8221; reading does not mean that your catalytic converter is broken especially if it is brand new. Again, the error codes just means that they are not performing as efficient enough to meet OEM standards.

SOLUTION: There are three feasible options to solve this inefficiency problem
  1. Ignore.
  2. Spark Plug non-fouler (aka Spark Plug defouler)
  3. Software upgrade
-Ignore-Since the post catalytic converter oxygen sensors is purely for emission monitoring it does not in ANY way affect your fuel trim and car performance. Therefore, it is perfectly fine to ignore the check engine light.
-PRO: No time and resources wasted on fixing problem
-CON: Annoying check engine light

-Software Upgrade-Software upgrade from major tuning companies will flash your DME to remove the ***8220;catalytic efficiency***8221; monitoring feature.
-PRO: Fast and requires no hardware/equipment modification to exhaust systems
-CON: Expensive

-Spark Plug non-fouler (aka Spark Plug defouler)-By installing the spark plug non-fouler, you are in essence moving the rear 02 sensor out of the direct flow of the exhaust stream/flow. By doing so, you are tricking the 02 sensor will an inaccurate reading. Since the 02 sensors is not directly in the path of the exhaust fumes, it can not accurate measure the exhaust fumes.
-PRO- Inexpensive
-CON- None

HOW:

People aftermarket headers w/o cats​

Go to Autozone and buy a pair of 18mm long and short ***8220;Spark Plug Non-Fouler.***8221;
Brand: HELP!
Part Number: 42009 (short) and 42002 (long)
Price: $3.50 for 42009 and $3.50 for 42002



Modify the short spark plug non-fouler (P/N 42009) to make the hole bigger in order for the oxygen***8217;s sensor tip to fit comfortable inside the spark plug non-fouler


Install your 02 sensors as followed:
O2 sensor, modified short fouler, long short fouler.

You are using two non-fouler to increase the distant between the exhaust fumes and the 02 sensors.



People with aftermarket headers and cats

Since you already have cats, you don***8217;t need to move the oxygen sensor out of the direct exhaust fumes as much as the people without cats.

Go to Autozone and buy a pair of 18mm long ***8220;Spark Plug Non-Fouler.***8221;
Brand: HELP!
Part Number: 42002 (long)
Prce: $3.50

.
NOTE: The package only comes with 2 non-fouler. In the picture above, there are 3non-fouler as reference only to help illustrate what a non-fouler looks like from different perspectives

Install your 02 sensors as followed:
O2 sensor, long short fouler.

NOTE: You might need to modify the long spark plug non-fouler (P/N 42002) if your 02 sensor***8217;s tip doesn***8217;t sit properly inside the spark plug non-fouler.

NOTES:
The oxygen sensor shown in picture is a pre-cat and NOT a post-cat. Only used as reference to help illustrate installing the non-fouler into the sensor.

When installing cats, you do not need to extend your o2 sensor. Simply re-wire the 02 sensor wire harness inside the engine comparment. This will give you an additional 3-4 feet of wire.


I hope this helps. Post your questions here if you have any. I am willing to help any fanatics with this modifications via online or in person for free.
 

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Do you think this will work on my 2003 530I? It has Dinan CAI, software, header, and Supersprint cat back exhaust system. I am getting CEL for running without cat. Thanks
 

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Discussion Starter #3
Do you think this will work on my 2003 530I? It has Dinan CAI, software, header, and Supersprint cat back exhaust system. I am getting CEL for running without cat. Thanks

This modification is non car/make specific. therefore, it will work for any car. the concept is the same. You are removing the post-cats o2 sensors out of the direct flow of the exhaust fumes/stream to trick oxygen sensor.
 

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I'm getting the aftermarket cats and post cat O2's installed this week. If it still throws the CEL, I'll look into doing this. Great write up!
 

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Discussion Starter #5
UPDATE:

I recently upgraded to headers. Because I am from California, installing Cats is a must due to the strict emission laws. However, even with the cats installed, I was getting the check engine light. After doing some research, I conducted the defouler trick.

After peforming this fix, my car has logged over 200 miles and my check engine light hasn't come back once. I scanned my car for hidden error codes with my Peake Reader and it seems like the "inefficiency" codes is a thing of the past.

I have a better picture of the modified/drilled out defouler if anyone wants to see it. The hardest part is drilling out the darn suckers. It is tuff and you get metal shaving/shapnels in your eyes, ears, balls, and mouth.

Good luck with this DIY. Again, your mileage may vary depending on your car's setup.
 

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UPDATE:

I recently upgraded to headers. Because I am from California, installing Cats is a must due to the strict emission laws. However, even with the cats installed, I was getting the check engine light. After doing some research, I conducted the defouler trick.

After peforming this fix, my car has logged over 200 miles and my check engine light hasn't come back once. I scanned my car for hidden error codes with my Peake Reader and it seems like the "inefficiency" codes is a thing of the past.

I have a better picture of the modified/drilled out defouler if anyone wants to see it. The hardest part is drilling out the darn suckers. It is tuff and you get metal shaving/shapnels in your eyes, ears, balls, and mouth.

Good luck with this DIY. Again, your mileage may vary depending on your car's setup.
How? :rofl:

But seriously, did you use a drill press? Or at least a vice?
 

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Nice detailed and organized write up. This should help a lot of fanatics out.
 

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Discussion Starter #8
How? :rofl:

But seriously, did you use a drill press? Or at least a vice?
How? Because I was completely naked when I drilled the spark plug non fouler. Something about dremels and handy tools brings the wild manny side out of me :confused:

anyhow, all I used was a small drill bit and a sanding tip. The small drill bit is to drill the hole big enough for the sanding bit to fit over. This is not the best method. However, it was my only method since I didn't have any access to the huge azz drill bits and power tools.

Here are some updated pictures:

1) Before and after. What your modified non fouler should look like after you drill them


shameless plug for BMW F1 Motorsport :shhh:

2) Noticed how the spark plugs sit snuggly into the spark plug defouler. Again, you drill the defouler so that the oxygen sensor plug's tip can fit inside. If not, there is no way for you to screw on the 02 sensor since the hole is just too small.


shameless plug for UUC motorwerks :shhh:

3) different angles of the oxygen sensor tips installed in a modified non fouler.




 

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Discussion Starter #10
here is two pictures of the spark plug defouler being installed on my exhaust system



 

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i got cats with my after market headers and no CEL, but the only thing is my cats freaking scrape over speedbumps. i wish they made 3" cats
 

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Discussion Starter #13

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I just installed the long non foulers on my car after drilling them out. By the way you need a 1/2" drill bit to drill it out large enough. It'll be wait and see if the light is thrown again. I'll keep people posted.
 

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Discussion Starter #15
I just installed the long non foulers on my car after drilling them out. By the way you need a 1/2" drill bit to drill it out large enough. It'll be wait and see if the light is thrown again. I'll keep people posted.
Cool. Please keep us posted. Show us some pictures of your drilling job also.

P.S. Are you stationed at fightertown, USA?
 

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Cool. Please keep us posted. Show us some pictures of your drilling job also.

P.S. Are you stationed at fightertown, USA?
Not stationed there, but I live about two miles from it. I get to hear 'em flying overhead every so often.

My drilling job looks exactly the same as your grinding job.
 

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I threw two codes on the way home from my girlfriends last night. Neither was for the catalytic efficiency below threshold. They were;

P1447 - Manufacturer Control Auxiliary emission Controls
P1190 - Manufacturer Control Fuel Air Metering

Any thoughts?
 

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Discussion Starter #18
I threw two codes on the way home from my girlfriends last night. Neither was for the catalytic efficiency below threshold. They were;

P1447 - Manufacturer Control Auxiliary emission Controls
P1190 - Manufacturer Control Fuel Air Metering

Any thoughts?
According to the Blentley P1190 is your Pre-Cat 02 sensor (bank1) going bad. Check the connector. Trying swapping the 02 sensors and see if the problem go away, stayed, or transferred with the swap.

p1447 is your emission control (ie Purge value or DM-TL Diagnostic Module Tank Leakage).
 

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According to the Blentley P1190 is your Pre-Cat 02 sensor (bank1) going bad. Check the connector. Trying swapping the 02 sensors and see if the problem go away, stayed, or transferred with the swap.

p1447 is your emission control (ie Purge value or DM-TL Diagnostic Module Tank Leakage).
Sweet, thank you! Looks like I'll be replacing my O2's (there originals with 113k miles on 'em). As far as the other two things. I guess I'll have to pull out my Bentley to do a little research and find out how to fix them, eh?
 
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