Ok...I got this tip from some of the local car enthusiasts...and this is one cheap O2 simulator.

It works, and there is no need to cut any wires or anything...very easy as well.
I personally have driven about 300 miles since, no CEL. So anybody who wants to run a test pipe...here is the mod you should do to stop the CEL...don't bother with the electronic ones with only some of them working...and not working all the time. These pics are from it being done STi, but I did it on my S, works just the same.





or


Those are the Spark plug, Anti-Foulers you'll need to do this..just pick them up at any auto parts store

 

Killer. Which part number did you use (there are two above)?

 

Umm, I don't get it? What does this accomplish other than moving the sensor back out of the direct flow? How big is the hole in the antifoulers originally? And correct me if I'm wrong but isn't that a catalytic converter in the pics.

 

 

I would give a little more time before claiming this to work. The codes for a Catalyst failure take some time before they are stored. The WRX pictured has a Convertor, weather or not it functions I don't know. I'm a little skeptical of this tricking the PCM simply by moving the 02 farther out of the exhaust flow.

 

I'll let you guys know...this is actually something Evo guys are doing as well...

The STi, in the pic is a guy I know named Matt...its a high-flow cat in the picture. He has had this done for 3000+ miles, and yes, a high flow cat will set off the CEL in their cars (says him). What this does, is it stops the O2 sensor from seeing as much exhaust...nm, here's this...

Pulled from Evolutionm.net

Quote:
I don't think this has been mentioned in the Evoutionm forums yet, but I've had a lot of success with a "mechanical" method that basically only allows the 2nd O2 to see a very small amount of exhaust gas, which it in turn translates this as a working cat. Therefore not tripping the CEL even with a cat bypass. I'm not sure how some of the vendors who sell pipes with guarantees do it, but I'd imagine it is something similar.

Before installing this, my car used to set off the CEL on the 2nd key cycle after a few miles on the highway. After the installation of this piece, I havn't had a CEL yet. This included a 2500 mile drive down to California for 3 straight track days.

Here's how it to do it:

1) Buy a set of 18mm Spark Plug Anti Foul Adaptors from the autoparts store. I got my from Schucks/Kragen/Checker and it came in a pair in the little red "Help" packages. These things are designed for cars that are burning oil and fouling it's plugs.

2) Drill out the small hole of one of the plugs to 1/2" diameter. This will allow the O2 sensor to screw into the plug while a tiny bit of room surrounding the sensor.

3) Screw either 1 or both adaptors together into the 2nd O2 bug on the cat back. Carefully screw the O2 sensor in. Don't overtighten since the adaptors are now pretty thin walled due to the 1/2" drilling.

4) Reset ECU by pulling the 2 ECU fuses in the fuse box under the hood (20amp and 15amp).






The only reason you'd need to reset your ECU though, is if you currently had the CEL on. And there's a pic of one with a test-pipe for all you sceptical guys.

Anyway...I'll keep you updated on the my CEL...if you want, I could take a pic of my test-pipe with this done...but it really looks no different.
Anyway, I have driven from San Luis Obispo to Famoso raceway, done 4 passes, then back to San Luis with this...total of about 300 miles, if not slightly more...and probably starting the car up more then 10 times. I would assume the CEL would have gone off by now if it was going to? But like I said...I'll let you guys know.


ohh and I personally used 42002...but it doesn't matter

 

From Matt (guy that gave us these great pics ):

The reason a high flow cat on the STi will STILL throw a P0420(cat inefficiency) code is because the factory exhaust system on the STi comes with TWO cats after the turbo...so basically my STi is essentially running with one less cat then what came on the factory exhaust which is the reason why it still is at risk of throwing a CEL with one high flow cat. Some STi's are fine with one high flow cat, some will still throw a CEL with one high flow cat...it's really case by case. In my case, the high flow cat on my STi still threw a P0420 CEL.

There you go...
Also, I drove the car more today...probably another 30miles and 4 starts...no CEL.

I'm just trying to help you guys save some money and not have to cut wires...

 

Slo,
Top suggestion, no sceptics here, I even understand the theory as the ECU looks for the second sensor to replicate the primary sensor readings but with slower fluctuations.

I will give it a go as my CEL is a constant worry.
I have never seen the Anti-foulers in the Uk, so any suggestions of a web based US supplier would be greatly apprciated.

 

Well, they cost about 4 bucks...how much would it be for me to ship it to you?

I'll do a quick UPS...ok NM...I did a check on a shipment to West Drayton (have a business card of an Indian Restaurant there)...51 buck...forget that...unless you really wanted to

 

Many thanks for the help so far Slo. You have PM.

The UPS option is way to steep, on principal but I am looking at options.