Hey all!

So, did a bit of research on this CEL I've been getting for a bit. This code is:

"Catalyst Efficiency Below Threshold (Bank 2)"

I had a weird thought, and maybe its just coincidence, but here it is:

Could this code (related to emissions and exhaust) have ANYTHING to do with the gundo hack I did a few months back?

We have just over 100k on this 2003 C4. Everything else runs great, but this CEL is getting annoying. I clear it and it stays gone for about a week.

If it was one thing that was bad for CERTAIN, I would just do that. But there are too many possibilities according to this forum and google...

Thanks in advance!

Bill

 

It shouldn't have anything to do with the Gundo Hack. It sounds like you need to replace catalytic converter. They do go bad and having 100k on the clock this would make sense.

 

Thanks for the reply!

Your email notification said "need to replace the O2 sensor", and then when I clicked the link to come here, you've edited it to say "replace the catalytic converter"...

So what made you change your post? Just curious. I'd LOVE to be able to test the item (either the O2 or cat) before buying a new one.

I'm reading a few posts about "It might be this part instead", and didn't want to start paying for things that aren't broken.

Thanks again! Either way I guess I can eliminate the gundo hack as the issue.

 

I changed it because I was thinking if it was an O2 sensor it would/should throw a different code indicating O2 sensor is bad. I think what's happening here is the O2 sensor is picking up that the cat is not working correctly and the emissions levels are too high on one or all of these carbon monoxide (a poisonous gas) nitrogen oxides (a cause of smog and acid rain) hydrocarbons (a cause of smog)

 

Lived with an intermittent P0430 for a number of years with my Boxster.

The diagnostic guidelines say something to the effect if the P0430 (or P0420 on the other bank) code is accompanied by aging O2 sensor codes to replace the indicated sensors and road test the vehicle. If the converter error returns replace the indicated converter.

In my car's case the converter "brick" was loose and would occasionally I guess get out of position that exhaust gas flow was less than optimum and affect the conveter's efficiency.

But the converter worked well enough to pass CA smog test more than once.

I eventually tired of the knocking when cold and the buzzing when hot and replaced both converters with ones I bought at a Porsche salvage business. The new converter is quiet and and the P0430 error code has not reappeared.

I do not think it will help much but I found it helped some, that is kept the error from appearing as often, and that was to switch from discount gasoline to Shell, but I suspect Chevron would be just as good and possibly better for reasons I won't go into now.

While running Shell gas the error appeared less frequently it still appeared once in a while, so it was not the cure. Replacement was the cure for the error.

 

Thanks Macster!

About a month after I did the gundo hack and reinstalled the exhaust, I heard a little "rattle". Figured it was just a loose heat shield (and haven't been around to tighten it). Its on the drivers side though, and I think "bank 2" is the passenger side...?

I think I will first try the O2 sensors. Wondering if I swapped them left to right, would that throw a different code if it was a bad sensor?

If I replace both, then at least I know for sure its not that I guess.

Thanks all!

 

I've had the hack now for 4 years with no issues, it could have just been coincidence. I use nothing but Shell