2001 SS

OK I've got a CAI by Spectre that was on the car when I bought it. I have put on an after market CAT by Evan Fischer after the OEM was plugged. I have put in a spark plug defouler and still the P0420 code keeps coming back.

Is there any way at all possible that the front O2 sensor could be bad? The only reason I ask is that when I bought it I bought an A/C Delco but it was "used like new in original packaging" off Amazon and I'm starting to wonder if that is the root of my problem? I'm not sure though if the front O2 sensor can play a part in that code or not? Or is it ALL the rear O2 sensor and the reading its getting? I'm sure the CAT is not plugged again. I'm out of things to try here short of tuning the PCM and I can't be without my car for the time it would take to get it done.

I hate having the light illuminated 'cause if I get another issue I won't know it because the damn light is lit up all the time from this friggin' P0420 code. Now according to this: I am getting this:

But how do I fix it? LOL

 

It's very common that a non-oem cat can cause this problem.

Some are successful with the spark plug non-fouler and others are not. Deleting the code in the tuning of the PCM guarantees it will be gone for good. This is one of a couple BASIC tuning options I offer. Here's my thread regarding PCM tuning I am willing to do:
https://montecarloforum.com/forum/pr...-3100-a-42773/

 

Test your O2 sensors. Even though you may not have a code for one of them, the carbon build up on one or the other can alter the voltage reading received by the PCM and cause the P0420 code. Most manufacturers recommend changing them at 45,000 miles for this reason.

 

Thanks guys. I guess I could always pick up an extra PCM but I'll try to test these O2 sensors first.

 

OK so what if I have the CAT cut out all together? Will I still throw this code? Is there anything else I'll have to do if I eliminate the CAT?

 

One thing that I have done is simply used an on emulator it tricks the car into thinking the normal cat is running even tho I'm running a zzp one

 

I had thought about that so that would be this: Rear O2 Emulator: 3800 Performance

Now let me ask you and maybe you can't answer but will this guarantee that the code will be gone? I hate to keep throwing money at this to get rid of this code but if this will do it once and for all I will pick one of these up. Before I do though is there any way the code can still pop up? Can I use this trick and still run my aftermarket CAT?

Also what happens to the bung hole in the pipe? Do you just leave it open? Do you cut the pig tail off the existing O2 and leave it in the bung hole?

Thanks for bearing with me on this.

 

I've never used the O2 emulator, but for those who have, I have heard it works without fail. You would need to put something in the O2 bung (even if it's the actual O2 sensor).

I do not have first hand experience with the emulator. I have no idea if they ever fail or any other potential pitfalls.

My P0420 code has been deleted in the PCM programming. If my emissions check ever wants to inspect my cat, they will find the cat AND the rear O2 sensor, so everything appears as it should. I know for a fact, you tune the code out and it's gone forever.

 

I can testify to this. I have an aftermarket zzp downpipe 2.5 and what I had the shop to is plug the of hole. They said they have plugs just for this. And I'm running the of emulator I have never had a p0440 code pop up at all. I'd say go for it. But they may b a tad bit hard to find. I got lucky and got mines off a member of the forum for pretty cheap

 

Jason and everyone interested. I've Ordered the O2 Eliminator to cure my P0420 Woes. I can't have Ol Yella down while my PCM would be off to Jason. I can't invest in a spare one yet but I will by Christmas. In the mean time I'm hoping this will work so I can get Ol Yella through NJ Inspection!
I will post the results!