Engine Drivetrain 1st Gen Cooper S P2096 even after installing new O2 sensors

So Ive been driving around with this code since buying this car. I've had to recently tackle it because I've got an emissions test to pass.

Since I was replacing one I went ahead and replaced both O2 sensors.

After clearing the codes I thought I'd seen the last of P2096.
Tomorrow I'm going to get tested and pulled the Mini out of the garage to wash it.
Wouldn't you know it, the code came back.

So, aside from the usual suspects (which I'll test for) I noticed the following.
I have a custom header and exhaust system and the rear O2 sensor has an extender on it to clear the exhaust pipe and not hit the body of the car.
What I noticed about the extension is that it wasn't a straight through pipe. It has a tiny hole for the exhaust to get to it.

Here is a quick sketch I made of the extender.



The little hole is only about 3 or 4 mm wide. Would this cause this problem?

 

Sorry i wasn't clear. The hole in the pipe is attached the exhaust pipe. Thats how the O2 sensor can sample the exhaust gases.

So instead of being directly in the exhaust stream it has to come through this small hole.

And Dave, i'm using TorquePro. So you think its possible ive corrected the original issue and the actual code needs clearing?

 

Hi Joker. I'm not sure I understand what you're suggesting I do. With a meter, how would I measure the resistance of the O2 sensor> Not while it's in use I'm guessing. If while running how would I do that?

I can remove the O2 sensors and measure the resistance easily, but these are brad new. I've never had experience with them being bad right out of the box. But I guess anything is possible.

 

Hehe Joker, yeah, I'm a tech, but in a different field! In any case, I'll pop the O2 sensors back out to check them.
Since I couldn't see any cracks or pin holes in the exhaust doesn't mean there isn't any, so I'm trying to figure the easiest way to test it. Such as pressurizing the pipe and using soapy water. I have a halloween smoke machine but that could get messy.

Also, I'm just assuming that this code will fail me on my emissions test. Will it actually?
It's the only code I've got at the moment.

 

So I took the post cat o2 sensor out and tested it. Heater wires are fine, the ground to feed was find at temp, just like the pre cat.

I don't have a way to test it while the car is running without possibly causing damage to the wires. So I didn't do that.

I did find a small exhaust leak just before the cat and welded it shut. Couldn't find any other leaks up stream. I did this by plugging up the exhaust pipe and pressurizing the exhaust system and then went along it with soapy water.
Found a couple down stream leaks that I'll fix, but those would not have anything to do with the o2 sensors.

The Exhaust manifold seemed fine, I couldn't detect any leaks there but then I could not get all the way around the manifold flange to test it. I did not however hear any noise, whistling coming from the flange while the system was pressurized.

Wish I had a smoke tester on hand. Might try that later.

For now, I have what seems like perfectly good o2 sensors telling me that the exhaust gases are lean and I'm not seeing anywhere between the upstream o2 sensor and post cat sensor that would introduce more o2.

A little more about the post cat o2 sensor. Here is how it's mounted:



The post cat sensor is basically right off the rear of the cat. Kinda odd to me.

I also opened up that pin hole that it was sampling the exhaust gases from to about 20mm now. Could go another 5 mm and that would be about as big as the interior diameter of the pipe.

Kind of at a loss now. If the up stream o2 sensor is fine how could the down stream sensor read lean...unless the cat is bad.

Ideas? And how would I test the cat to know?

Thanks and I'm off to drink a bunch of beers.

 

The L pipe came with the car. The header did too. From what I've found, it's a CMC header, ceramic coated interior and exterior coating, and some kind of race cat.

That's the best I got.

As for being able to remove the L pipe, I can. But the o2 sensor won't fit back on without hitting and rubbing against the car.
I could try it to see if the code clears.

I don't have access to the Bav Tech or other real tool to clear the codes. So, I just ordered one.

 

For the BavTech I bought the single car version.
I don't think I will need it for other cars...but I should have purchased the 3 Vin version.

Do you guys know if it's possible to buy additional licenses from them? I'll jump back on their site to check.

 

Thanks for the help on the phone Dave!
The BavTech tool really is pretty slick. And easy to use!

I got my code cleared along with a few others that I had and didn't know about!

Hopefully this takes care of this issue and I pass emissions tomorrow morning without problem!