Reoccuring OBD-2 Code

[Brian95SVT]

Ok, I have been getting this code and I'm not sure what else it could be. It's P0403 and it said something about catalysis below threshold. Now I have been searching online and all I can find are EGR related problems but I have already replaced my EGR Valve. I replaced all my o2 sensors. I've replaced all my spark plugs. I'm dumbfounded. When I'm driving my car and the check engine is ON it doesn't preform like it should, doesn't pull has hard as it should, etc. I went to the local Advanced Auto and deleted the code tonight then on the way home got on her and she pulled hard like it should. But I know this light will come back on tomorrow or within the next few days and I want to figure out what it is...... Any suggestions???!?!?!?

Thanks, and sorry for all of you who know me and have been wondering where I've been... I will post another thread soon and explain.

-Brian

 

[Red96GT]

My car threw the same code and it was from the catted X pipe. I got MIL eliminators and hopefully that will keep it off.

 

[Brian95SVT]

The only thing about it is others who have the same catted x-pipe as I do said that they didn't need to get MIL eliminators. They said I shouldn't need them...

 

[Red96GT]

yeah EVERYONE said the same thing to me too but mine came on. Oh, and I'm pretty sure the light is just a dummy light so it shouldn't be affecting your performance at all.

 

[Brian95SVT]

Well the light comes on when there is a problem. Hence the light ha. Because your computer is making you run leaner than usual to compensate for the problem, in this case. The second I erased the codes and the light when out, it pulled harder. So that's factual... I guess I can try the MIL eliminators but I don't think they will help because it's not saying ANYTHING about o2 sensors... and that's what the MILs replace. Before when the o2s and the below threshold were both coming up then maybe MILs but now that I replaced all the o2s and the below threshold is still there... makes me think otherwise...

Just my thoughts... could be wrong though.

 

[Red96GT]

My code was exactly "cat. converters functioning below threshold." This code is a result of the oxygen sensor sending the wrong voltage back to the ECU. Didn't notice any adverse performance change. Drove like that for 4 months. Bought MIL eliminators. Light went out. Never felt any change with the car... That's my experience. It'd be nice to know if the O2 sensors actually affect the Air/Fuel as I've heard both sides.

 

[Brian95SVT]

Yeah. I know that before I got my o2s changed it was running sluggish. That slightly went away. Changed out my spark plugs and it made it a good amount better but the light is still on saying Catalysis below threshold, bank 2 and I'm not sure what else to check... but it IS making my car not be able to preform as well as it SHOULD.

This is my mod list just incase anyone reads this and wants to know:
Re-manufactured Jasper 4.6L V8 for 1996 Mustang GT *which I own hah*
BBK Short tube headers
BBK Catted X-pipe
Flowmaster cat-back
PI Intake
MAC Underdrive pullies
New spark plugs
New EGR Valve
New o2 sensors

 

[Brian95SVT]

Anyone?

 

[xsoutherngun89x]

its your x pipe. get either MILS or a Tuner like i did. i noticed teh same thing with my UPR o/r x. went really lean so you might foul a plug like i did.

 

[Brian95SVT]

That's with O/R X-Pipes. People said that with Catted X-Pipes I shouldn't have that problem..... guess they were wrong. I'ma be picking up a set of MILs here soon.
Now I have to get all 4 right? Cuz say if I just got 2 MILs, the other two o2s would still be sending signals to the ECM saying there is a problem.... right?

 

[xsoutherngun89x]

no the o2's before the cats are fine, its your o2's after the cat that are giving you this issue. might wanna save up and get a tuner, they can cut those rears off and you can do a whole bunch of other stuff. but if you dont wanna shell out that cash right now, DropTopPony has a set he is selling in the classifieds

 

[Brian95SVT]

no the o2's before the cats are fine, its your o2's after the cat that are giving you this issue. might wanna save up and get a tuner, they can cut those rears off and you can do a whole bunch of other stuff. but if you dont wanna shell out that cash right now, droptopony has a set he is seeling in the classifieds

well it said bank 2... are you sure it's only the two after the cat and if i get just those two the other two before the cat will be fine? i don't have the money for a tuner, i have other things i have to fix first.... tuner will come later down the road...

 

[xsoutherngun89x]

yup, the 2 before the cat arent affected by the presence(or lack there of) of cats. it is the one that tells your engine how its performing. The rear o2's are the one that tells the comp, whoa somethin aint right, and leans out the mix. if you also have the PI intake this will even be felt greater. Ill forwarn you though, MILS dont always fix the problem. Ive seen people that have bought em and they didnt work. The MILS should get rid of the code fine though. Just think of it like this, your goin from 6 restrictive cats to 2 high flow units, the comp is gonna think somethin isnt right.

 

[Brian95SVT]

I want a permant fix... what do you suggest?

 

[xsoutherngun89x]

SCT Xcal 3 from lasota racing technologies. You would benefit greatly form one. Your an auot so you could adjust shift points/firmness of those shifts too. Plus i knocked off almost 4 tenths in the quarter. My car was running super lean cause the PI intake and o/r x. You dont need one, but if your gonna get into the car seriously(like gears, converter, dynoe tune, etc) you could benefit greatly from it. If you have issues that need to be fixed asap the tuner can wait.

Also a tuner isnt "necessary" im not gonna BS you there. They arent that cheap but i dont know what other mod can knock off 4 tenths at 375 bucks and 10 minutes to upload your tune. The light isnt a huge deal. just watch your plugs and be easy till you can get either MILS or a tuner cause the setup you have(i had the o/r x and a PI intake) is similar to mine and i was quite lean. The CEL is just annoyin

 

[Brian95SVT]

Well there is a problem, I know it for a fact. It runs a lot better sometimes and if it's leaning me out then that's a problem ahahah
I want to get rid of the problem. Everyone says MILs and it will fix it but you're saying otherwise..

 

[jfor441]

DropTopPony is selling a set if Steed MILs for 50 bucks. Buy them from and see if that fixes your issue. It is cheap and might fix what problems you are seeing.

 

[Brian95SVT]

Ok. Thanks.

 

[xsoutherngun89x]

Well there is a problem, I know it for a fact. It runs a lot better sometimes and if it's leaning me out then that's a problem ahahah
I want to get rid of the problem. Everyone says MILs and it will fix it but you're saying otherwise..

oh no no, lol. MILS will fix the issue. lol. i just said that some people have had issues but most have never had a problem with em. they WILL work. i never intended to make you think they wouldnt work, my bad

 

[xsoutherngun89x]

DropTopPony is selling a set if Steed MILs for 50 bucks. Buy them from and see if that fixes your issue. It is cheap and might fix what problems you are seeing.

lol i told him that earlier on Josh. i think thats the best route for him to go as of now.