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anothernord
07-04-2009, 05:02 PM
IMPORTANT UPDATE: It turns out that one spacer is not enough to stop the CEL from reoccuring. Just drill out the other spacer and install it too.



Credit for the original fix goes to Peaty of Scoobymods.

If you have an upgraded or aftermarket exhaust installed, you might get the P0420 CEL since the rear O2 sensor is seeing more flow and thinks something is wrong with the catalytic converter. By installing a rear O2 spacer, you can reduce the amount of flow the rear O2 gets, and stop the CEL.

Once again, I am not responsible for anything you do to harm anything or anyone.

Tools needed:
-22mm wrench (or 22mm open sided socket w/ breaker bar)
-1/2 inch drill bit
-1/4 inch drill bit (anything in this range will work; you just need to open up the second spacer for more flow)
-Drill (drill press would be way easier)
-Vice
-Jack/jackstands

Items/Materials:
-Help! Spark Plug Non-Fouler part # 42002 (#42009 works as well)
-PB blaster (if you can't get the sensor out)
-30 minutes (you'll never get this back)

1. Go and buy this. Most auto parts stores have them: (picture credit: Peaty of Scoobymods)

https://sl-i.net/FORUM/images/imported/2009/07/attachment-1.jpg

2. Get your 1/2 inch drill bit, and drill out ONE of the two spacers while it is held in a vice. This must be done so the sensor head can screw inside the spacer and have room around it to allow gasses to flow into the sensor. If your bit is dull you might have to drill successively larger holes up to 1/2 inch. A drill press would make this step a whole lot easier.

3. Take your second O2 spacer and drill it out just a little with a 1/4 bit or similar.

https://sl-i.net/FORUM/images/imported/2009/07/IMG_3394-1.jpg

4. Jack up your car, place it securely on jackstands, and chock the rear wheels.

5. Soak the rear O2 sensor in PB blaster. This is an optional step but it makes getting the sensor out a lot easier.

6. Using the 22mm wrench, unbolt the rear O2 sensor.

6. Now screw in your bored out spacers into the catalytic converter first, and tighten them down. Make sure the spacer that the 02 sensor will go into is on the top.

7. Thread and torque the sensor down into the spacers. The final result should look like this if you used one of the spacers (2 is recommended):

https://sl-i.net/FORUM/images/imported/2009/07/IMG_3388-1.jpg

8. Reset the ECU by pulling the negative battery cable, stepping on the brake, and then letting it sit for a while (20 mins usually works). If you still have the P0420 code, install the other spacer in between the cat and first spacer. If you get a P0139 instead from the 2nd spacer, it probably isn't getting enough flow, so drill out the hole in the second spacer as well.

1-3-2-4
08-29-2009, 11:09 PM
The funny thing with the 1/4 bit and the fouler is the bit will fit right in the hole without drilling..

RSKwannabe
05-08-2010, 03:54 PM
I was very happy to see this as I have had the dreaded CE light ever since I modded some exhaust parts years ago. I first added the Borla Header and would get sporadic CE lights. I used to reset whenever I got the warning. Then a year or so later, I added the Strommung midpipe and it has been consistent CE light. I first tried the wiring trick and when that did not work the bung attachment. All items were purchased from Boxer4racing. I also changed the O2 sensor. No complaints with the exhaust parts as I feel a definite (albeit slight) improvement in sound and sotp pull. Although the header did get a leak last year, it was quickly patched up by local shop. Guess I could have gone back to Borla with 1M mile warranty but it seemed more of a hassle than spending $60 bucks for the quick weld job. Trouble is neither fix worked.

Question: The bung extension is approx 2" or roughly the length of 2x 42002. The parts described above are about 7/8" for 42002 and 3/4" for 42009. Is it possible that the CE light is going since there is not enough flow based on the distance of the Boxer4racing bung? Thanks!

anothernord
05-15-2010, 07:08 PM
Right, you can get a CEL if the sensor is getting restricted too much. With my setup, I had to drill out the second extension.

TGX4776
05-15-2010, 07:14 PM
IMPORTANT UPDATE: It turns out that one spacer is not enough to stop the CEL from reoccuring. Just drill out the other spacer and install it too.


You mena one for the front and one for the back?

anothernord
05-15-2010, 07:24 PM
IMPORTANT UPDATE: It turns out that one spacer is not enough to stop the CEL from reoccuring. Just drill out the other spacer and install it too.


You mena one for the front and one for the back?

No, stack two spacers on the rear sensor. The code is only triggered by the rear sensor.

TGX4776
05-15-2010, 07:29 PM
ok, also do you know if the front and rear o2 sensors are the same part?

anothernord
05-15-2010, 07:39 PM
Almost 100% positive that they are different.

TGX4776
05-15-2010, 07:48 PM
damn, guess I have to go genuine Subaru parts then.

TGX4776
05-15-2010, 07:59 PM
heh, forgot about autozone to search for parts. If i were to use a single Vibrant universal hi flow cat i place on sensor before the cat and one right after correct?

Sorry to jack your thread.

RSKwannabe
05-15-2010, 11:16 PM
Where exactly are the two O2 sensors? I think I tried to look for a second one years ago and was old that BE only had one. The bung is installed in the midpipe section.

jey
05-17-2010, 12:13 PM
One is before the cat, one is after

hrdrifter
05-18-2010, 05:03 PM
So you drill out the spacer and let the o2 sensor make its own threads?

anothernord
05-18-2010, 05:06 PM
The spacer already has threads for the sensor, but the head of the sensor needs room inside the spacer, which is why it must be drilled out.

hrdrifter
05-18-2010, 05:22 PM
The spacer already has threads for the sensor, but the head of the sensor needs room inside the spacer, which is why it must be drilled out.


Ohh now it makes sense. Thanks.

hrdrifter
05-20-2010, 09:40 PM
I did this today. Took about 45 minutes including taking the sensor out. I used a non fouler from napa, 730-2443 is the part number if anyone wants to know.

jockstar
10-27-2010, 09:16 AM
I did this today, took about 30 minutes. I have another spark plug anti fouler that I turned on a lathe with a 1/2 inch bit if anyone needs it let me know, I can actually have an infinite amount of these and the hole is true as possible.

TGX4776
10-27-2010, 09:52 AM
mine will eb done today if the guy doing the exhaust install does it.