Now I understand X code enough to make inspection bits patch as in CT9A if there is enough interest and some volunteer to test it

 

It would be really cool if you could disable the rear o2 CEL. Specifically, both the sensor in the downpipe before the cat, and the sensor in the cat. My guess is the combination of these two are used to trigger the rear o2 CEL. This would allow using a wideband in the stock downpipe (before the cat) in place of the stock o2 sensor without triggering a CEL

 

The first sensor is for closed loop AFR control (during cruise conditions). Its only the one in the cat that needs to be disabled.

 

- disable the rear o2 CEL. Can test on edm evo

 

mrfred, when you say first sensor, do you mean the upstream o2? The evo x has 3 sensors. One upstream, one in the downpipe before the cat, and one in the cat section itself. This is nice because the middle o2 sensor in the downpipe can be replaced with a wideband for logging purposes (pre-cat).

 

ok, I get it now. There are references in the FSM to an offset O2 sensor value. I always thought this was some sort of reference voltage built into the post-cat O2 sensor, but it must be the O2 sensor just before the cat. They must use this as a precat reference value. (They use the 1st O2 sensor for this in the Evo 7/8/9.) Thanks. This is helpful in understanding the disassem.

 

Three? Since when?

- Bryan

 

Double post fail.

 

Hmm.

I thought there were only two, pre and post cat. This is news to me, and none of the OBD scans indicate more than two... Though I haven't seen them physically (except for the rear one)

Are you sure?

 

Oops, maybe I'm confused then - I thought there was an o2 sensor upstream before the turbo? There are definitely two post-turbo (one in the downpipe, one in the cat), but is there none upstream from that?

EDIT: Yup, I'm wrong. Sorry for the confusion. I've never had a car that had an upstream (front) o2 sensor so far back. I always assumed there was another upstream sensor somewhere in the engine bay.

 

there is only 2

that offset is the voltage offset u see in the code mrfred!

you can do a rear02 disable by flipping bit6 of ecu-options-2 (ie second last bit)

you will have to remove the sensor thou, as its heated and once you flip that bit it disables the heater...

 

Hi Tephra,

Can you confirm this solution for the X ?
If no : you know how to for the X ?

Thank's
Patrick

 

if you send me a front pipe I can test it out

atm my car is stock so I dont get an exhaust cel's hehe

ill be testing the removal of the rear02 over the weekend - i need to install a wb into that hole

 

Very interested in the rear o2 disabling. Keep us posted tephra!

 

USDM removal of rear o2 and install of a Wideband works fine!

killed it via options #2 no cel