So I've got some questions...hoping you have answers - Honda Prelude Forum

Agbrodey23 · 10-03-2008, 04:55 PM

So I installed new megan racing headers and a greddy ti-c cat back exhaust system on my 01 SH, and now my CEL is throwing P0133(O2 sensor slow response) and P0420(cat converter below threshold) codes. Also I have been reading up on the black soot that is forming on my back bumper accompannied with a slight gassy smell from the exhaust fumes and the consensus is that this is typical for Preludes in general.

My questions are: Will erasing the codes keep them from coming back on? I reset the ECU and the light returns, but will erasing them with an OBD II scanner get rid of them. And are there any downsides to this black residue besides appearances and are there any ways to fix it? Thanks

prepreludesh · 10-03-2008, 05:28 PM

i have a quick response to this...

I have (had) that similar setup... Megan Racing Header, Random Technologies Cat. and Greddy Evo 2 cat back. The black soot is a part of life man... Anything with wide open pipe and nothing to really catch the unburnt fuel just quickens the amount of soot collection on your rear bumper. I would find it would be instantly dirty after a 10 mile cruise after a carwash (gotta show it off!). There's really nothing to do about it and I think we all live with this...

As for you throwing a code, I never had that happen to me, and if I saw the CEL come on, I pulled the fuse, waited 15 seconds and put it back in and I was usually good for another oil change. Gas mileage stayed pretty good too (within normal levels).

You might have that first code throwing because did you notice how much taller the bung is for the O2 sensor on the headers that Megan Racing makes? I know my AEM wideband barely had anything showing in the exhaust stream, although it does it okay. Maybe your O2 sensor is the same way and a factory sensor is just more touchy to not being in the direct exhaust stream?

I can't conclusively give you an answer on those codes, but if you change your O2 sensors (although expensive) you'll have to tell me if it does you any good. They do go bad you know.

itzroyal · 10-03-2008, 08:34 PM

From what my friend at honda told me, changing your cat will make your CEL come on. The reason behind this is because the high flow cat will allow more air to pass thru, which will trigger the CEL to come on with the code. You are still using your stock o2 sensor and is not adapting to the higher air flow from the cat.

conjur · 10-03-2008, 11:11 PM

I would seguest resetting the ECU to see if the codes come back; if they do, double-check the O2 sensors; make sure their plugged all of the way in; tight in the bung; and that none of the wires are bare, or possibly shorting out..

If everything checks out, and you still get the codes, you could try having a muffler shop weld a shorter bung for the Primary O2 Sensor; or replace the Primary O2 Sensor...

disclaimer: don't take my advice without getting a second opinion; I've never personally had this problem.

As for the black soot; the way I got around this, is by getting exhaust "tips", that were meant to face up, and mounting them upside down, so they blow the exhaust down, away from the bumper.... I still get a buildup over time, but it is not near as bad as when the tips were facing up! It looks a little funny, but it works.. *shrug*

V/r,
Mike

Agbrodey23 · 10-04-2008, 12:34 AM

Thanks a lot for the quick responses guys. I have tried resetting the ECU multiple times and the codes still return, but I am going to have to take a look at the O2 sensor and make sure it is not bad. But I'm pretty sure that nothing is wrong with either O2 or the Cat. I think its just like u said its the factory sensors not adapting to the new amount of exhaust flow. So, as long as everything is mechanically sound, is it possible to get rid of the codes by erasing them with scanner?

itzroyal · 10-04-2008, 07:54 AM

The codes will continuously to keep coming back up. My friend had a similar problem with his EVO. He was told to get a bosch o2 sensor and his CEL hasn't come on yet. You may want to look into that.

Sol Badguy · 10-04-2008, 11:46 AM

Head over to Kingmotorsports.com and get the O2 sensor plug, it will make the rear O2 sensor read the correct amount of air. I think it's only $35. good luck