Anybody with a cat delete, and/or sport cats. What have you done to get the MIL light off?
I did find a write up on a Mustang board on a capacitor and resistor modification for the rear O2 sensors but have not had the opportunity to do it yet.

 

I haven't done it on my current car but have been catless on two prior vehicles. I generally had a new O2 sensor bung welded in that was L shaped and took the sensor out of the direct exhaust stream.

there are tons of variants but they looked like this IIRC:

Weapon-RŽ 963-111-101 - CEL Eliminator

 

As noted above the O2 bung extenders are going to be your best bet. You can use straight extenders or the 90 degree ones. I think the 90 degree extenders are used because of clearance issues and the exhaust tunnel in most cars. I'm not sure if the old resistor/capacitor trick will work on the newer cars.

This is what I did on my 2006 Audi S4 to get around the CEL:

How To: Install An O2 Sensor Non Fouler to Eliminate a Check Engine Light with Pics - Chevrolet Colorado & GMC Canyon Forum

 

Here us a pic to give you an idea.... This worked for my cat delete... Had a CEL light on for a bit ...but it was just a pin hole in the weld.... Had to drive for a bit of cycles to get a passable MIL status for state inspection .

 

Here's another .

 

That's pretty much the same as mine except I move the sensor a little further down stream.. I drove for a while and upon several shut downs and start ups it cleared the light.

 

Are you just running the spacers/mini cats to go catless?

I've seen dyno charts which show the car running poorly due to the A/F ratio going skewed by poorly reading post cat o2 sensors - because they cant effectively read what is there... This actually negated the gains from going catless! Much better to just remap to a Euro2 tune - which removes the post cat o2 sensor from the equation.

I'm going to get some decent 200 cell cats to avoid the issue though and retain the standard setup - looking at HJS and Vibrant GESi units - probably the latter due to price and warranty!

 

Typically the rear O2 sensors only monitor if the cat is functioning. They don't have anything to do with Air/Fuel adjustments. Catless should not be a problem. Worst case the check engine light pops for the O2 not seeing a signal delay due to the missing cat. The ECU shouldn't change how the car runs if it doesn't see a cat.

 

Here's the thread I'm referring to:

https://www.jaguarforums.com/forum/f...-149353/page3/

Quoting from the post:

"You can see the lean patch on the red run, just after the transition to WOT. The minicats slow down the response time of the rear sensors, so the ECU can't get the fuelling right.
In addition to this, the owner of that car reported a major improvement to his highway economy, dropping from 9.8L/100km to 9.2L/100km, it was also evident on the tailpipes of the car, with the minicats the tailpipes would soot up quite quickly, with them gone the pipes were much cleaner."

 

I read through the thread. It is very interesting. As far as I knew the lower sensor was added for OBD2 cars to monitor the cats. I found this link that helps explain the function of the lower O2 a bit more:

http://www.team-bhp.com/forum/techni...l-engines.html

It would seem that the lower O2 will affect fueling slightly. It slightly richens the mixture to make the cat heat up faster, and it leans it a bit if the cat gets too hot. Basically it keeps the cat in the optimum temp range.

As far as running rich/lean it will depend on what you do with the lower sensors (spacers/minicats) and you'd have to confirm it on the dyno.

 

I guess I'm going to try the extensions first, before I cut into the o2 wiring.... We shall see.....

 

Just remapping to EURO 2, the rear O2 sensors should be on their places

 

No need to cut wires!

Yes it's true that the downstream sensors are also used to manage fuelling, they are not only for monitoring catalyst performance.

On the Jaguar engines this has been the case since the AJ-V8 was first introduced in 1996. And it applies to all vehicles since.

Trying to find a proper explanation is not so easy, but I did get something from a Denso document (the Jaguar gasoline engines used Denso ECU's up until around 2013 when they switched to Bosch, it also applies to the Bosch cars).

So this is it:



Basically the downstream sensors are used to control the "skip" which is like an over or under correction when there is a rapid change in the AFR.

Which is why the slow &/or incorrectly reading downstream sensors create problems. Some more info in this thread https://www.jaguarforums.com/forum/x...-remap-140980/
You can see the dyno charts with the AFR plots in that thread, also the pictures of the "minicats" or extensions which we took off the car.

The best way to solve P0420 & P0430 code problem when running high-flow or even no cats is to change the emissions setting of the ECU to the Euro 2 standard which disables the catalyst efficiency monitoring. This way the downstream sensors are still accurately measuring the oxygen content of the exhaust, and the fuelling "skip" correction is not affected.

Next option is for the P0420 & P0430 codes to be disabled in the ECU, most tuners can do this with their tuning software. The ECU still detects the "fault" with the cats but no longer sets the code or the CEL.

The minicats or extensions are probably the cheapest option because nobody has to touch the ECU, but you are no longer getting the correct fuelling because the sensors are simply not reading correctly.

Likewise for these "O2 sensor simulators" which are wired in between the sensors and ECU, you are giving the ECU wrong information. And it will adjust the fuelling based on wrong information.

 

Sorry to bring back the thread, but my current problem is related to the downstream probe.

I ordered caldoofy's 4-1 mid length headers, sport cats & exhaust, and I wish to know whether I should add extensions.

If there are measurement errors due to downstream extensions, wouldn't it be better to forego them? My main question: if you don't add downstream sensor extensions, is there any ill effect besides throwing cat codes? I can live with that, but not something that would i.e. trigger restricted performance mode.

L.E.: I have the dreaded, uncrackable 03-05 Denso ECU, so software tweaking is out of the question.