96 GT trouble code question........

CCM Power

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Recently my 96GT started giving me codes p0420 and p0430. They are "catalyst system efficiency below threshold" codes. Here is the thing. I did have a Hypertech powerchip on my computer but had to take it off because I put a 180 thermostat on the car which for some reason was causing the fan to run constantly. Shortly after I took the powerchip out I started to get these codes. I actually have a BBK catted h-pipe on it so I am still emissions legal. Do you think there is any connection with the now "stock" computer having a problem with my catted pipe? This is frustrating because of still being emissions legal but now Im getting these codes. Any help would be appreciated.
 

1996mustangGT

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i would try to get in contact with BBK
and see what they have to say about it...
i have a friend with flows and catted x and he was getting
check engine light, so ill ask him about what he did
 

CCM Power

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Thanks in advance for doing that for me. This is starting to get annoying now. My car drives fine. Sometimes when Im on the highway in 5th gear and maybe doing 60-70mph and i let off the gas it will buck a little bit. Im not sure why on that either. My Oxygen sensors are the originals with about 70,000 on them and my BBK h-pipe has about 30,000 on it but I would hope that my cats arent bad after only that low amount of mileage.
 
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scarface

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I had to run MIL eliminators with a catted hpipe. the ECU was still throwing the no cat code.
 

CCM Power

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The strange thing is that I have had this catted H-pipe on for about 3 years now and it seems weird that this would just start happening now all of a sudden.
 
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scarface

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did the programmer cut off the CEL? Mine was cutt off durring the tune.
 

CCM Power

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I ran the codes last night and the same two came up so I cleared them out,shut off my check engine light and checked everything over. I just find it hard to believe that two high flow converters could go bad at the same time and with low mileage on them or even have 2 O2 sensors go bad at the same time. Just out of curiosity, since there are 4 o2 sensors is it best to replace all 4 at the same time or just 2 if thats all you need?
 

1996mustangGT

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i would go ahead and replace all 4 just to be sure.
better to not have to run into problems with the
other 2 later.
and my friend actually got a o/r x pipe then just got MIL
eliminators, then had someone flash the computer or something
like that
 

CCM Power

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Actually, I've done a little more reading on the whole thing and found out that when I took the hypertech computer off my computer thats what did it. The stock computer is reading the high flow cats as not doing their job. Im going to get some MILs and that will clear it up along with pass inspection too. Since I will have those 2 o2 sensors off I will replace them right away too.
 
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scarface

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CCM Power said:
Actually, I've done a little more reading on the whole thing and found out that when I took the hypertech computer off my computer thats what did it.
Dude I said that very thing a few posts above.
scarface said:
did the programmer cut off the CEL?
 
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scarface

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ok...I though maybe you didnt understand what I was trying to say
 

CCM Power

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Thanks. Im telling ya............. I love my car but sometimes stuff like this is enough to make you want to pull your hair out! :nonono:
 
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scarface

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CCM Power said:
Thanks. Im telling ya............. I love my car but sometimes stuff like this is enough to make you want to pull your hair out! :nonono:
welcome to the joys of owning a stang :(
 

CCM Power

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scarface said:
CCM Power said:
Thanks. Im telling ya............. I love my car but sometimes stuff like this is enough to make you want to pull your hair out! :nonono:
welcome to the joys of owning a stang :(

Not so much the joys of owning a stang............more like the joys of modern technology with all these stupid computers in the cars nowadays! :rant:
 

1996mustangGT

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that is why if i ever change my engine im
seriously considering going to carb instead of efi
 

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