Hello all this is my first post on the forum. I recently installed exhaust headers on my 02 is300, obviously it threw a CEL light. I currently have defoulers with o2 sensors on all four sensors (bank 1 sensor 1 and 2/bank 2 sensor 1 and 2).

The current set up is after market headers(no cat) with stock y pipe (with cat).

So my question is which sensors should I put the defoulers on to clear the code.

UPDATE:
I found out that I was not supposed to put defoulers on primary sensors (Bank 1 and 2 sensor 1). I will remove defoulers from B1S1 and B2S1 and leave a defouler on B1S2. BUT what do I do with B2S2 (the o2 sensor on the ypipe)?

 

Good luck with that. I doubt you're going to get it to work and I'm not saying that to be an *** pirate. I'm saying that because the way that OEM ecu measures the 4 o2 sensors is pretty "special". I wouldn't expect that you an get any cheap device to simulate a properly running setup in this car. I could be wrong, but I don't think what you're suggesting is going to work to fix your problem.

 

I removed defoulers from B1S1 and B2S1 and left defoulers on B1S2 and B2S2; I then erased the code. The CEL stayed off for about almost 200 miles then came back on again for the same code. BUT the engine is running much better because the O2 sensors pre cat are reading correctly. been driving with the CEL code for a 400 miles now and nothing is wrong but does anyone know a permanant solution to this?

 

What shape are your defoulers / O2 spacers. The 90 degree bend ones seem to work better on IS300s. I know a few people using these

 

I ran catless headers before going NA-T for about 6 months with no engine light. As mentioned, the 90* extenders are the way to go. I ran them on just the down stream o2s. The 90* angle will really help them stay out of the system enough to not throw codes. The other option is to just put plugs in the down stream o2 bungholes and put bags/tape around the sensors and zip-tie them away from anything hot. I am doing this currently because I didn't see a need to make two more holes in my downpipe. But the sensors must remain plugged in to keep other codes from coming.

 

I don't know if putting a bag on the sensor is a great idea. They're heated which means they would melt the bag to the sensor and foul it..... or that's what I think would happen anyway.

@TrueGS300 - are you running a cat now on your turbo setup and if so, how do you have the o2 sensors configured in relation to the cat?