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I had previously removed the cat off my 05 GMC a while back and it set off the check engine light with a p0401 and p0404 code. I just had the computer flashed and updated because these codes were a common problem. Does anyone know if now I can remove the cat without having the same problem.
 

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If you have a Cali or a federal truck, you will set codes. You will need a Fingers Stick to block the code. This is also true for your EGR post.
 

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I have an 05 Cali truck - flowmaster exhaust, no cat and no codes. It's been over a year with this mod, do i need to get the egr blocker plate?
 

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My 05 didnt throw any codes with 5 inch exhaust not cat and a k&n intake
 

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2004.5 Lly Gmc

I've had no Kitty in now for about 2 months. I have had no codes set since doing this modification. Research I did prior to taking the cat out seemed to show that there was a about a 10 to 30 percent chance that a code would show up. Talking with the reps at my exhaust manufacturer Silverline they said they had customer instances of muffler installations with louvers facing toward pickup cab set codes assusming that they caused enough resistance to set a DTC code and theat when the mufflers were turned around the code wouldn't come up. Other research told me that about 1 in 10 LLY trucks set this code. This is an idea of my own that might cause it from not happening. The stock exhaust manifold on drivers side restricts air flow significantly. It only allows flow of the front two combustion chambers causing excess heat to the other two. I've installed the BD Supermax aftermarket manifold and I think this may allow more flow, not to mention balancing both sides of the engine. I haven't had to put the fingerstick on either, or may be I just had good luck. I also have and 80hp/200 ft lb flash tune by Dr. Performance. These are my treories. I also know that from my experience the low end shifts especially from 35 to 40 mph really smoothed up for me after this manifold install. I have 118,000 miles on my truck. Aaron
 

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I only get P0101 and this is with the FingerStick
 

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my 05 hasnt had any codes or lights. i have the egr unpluged and blocked as well as no cat. all these mods i have had for about 2 years now. i did buy it used from the dealer and the car-fax showed me it used to live in Utah... guess my truck isnt a CA/fed.
 

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kawimotoman837;1572989; said:
I had previously removed the cat off my 05 GMC a while back and it set off the check engine light with a p0401 and p0404 code. I just had the computer flashed and updated because these codes were a common problem. Does anyone know if now I can remove the cat without having the same problem.
You will have no problem. I have a NE emission truck (same as cali). Got the up date done, then installed turbo back MBRP Duals. I have never had SEL come on.
 

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Well the dealer installed my 4 in exaust system including the cat deleate pipe.. They had to update the computer to do away with the codes..

Arm:exactly:
 

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ARM;1576694; said:
Well the dealer installed my 4 in exaust system including the cat deleate pipe.. They had to update the computer to do away with the codes..

Arm:exactly:
Must be nice.
 

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ARM;1576694; said:
Well the dealer installed my 4 in exaust system including the cat deleate pipe.. They had to update the computer to do away with the codes..

Arm:exactly:
They (the dealer) removed your CAT? That's a BIG NO NO.
 

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Well how do you know you have a emission truck.. Yes a cali or federal, but is there any other way? I got mine out of Seattle, which came from Ohio at an auction. I am planing on getting an exhaust, (not sure which one yet, maybe Banks) and if I throw a code I have no way to reprogram it.
 

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AKDZL;1578809; said:
Well how do you know you have a emission truck.. Yes a cali or federal, but is there any other way? I got mine out of Seattle, which came from Ohio at an auction. I am planing on getting an exhaust, (not sure which one yet, maybe Banks) and if I throw a code I have no way to reprogram it.
A federal truck has a code of FE9 in your glove box build list. I'm not sure what the Cali code is off the top of my head. I'm sure someone will supply that info.
 

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bunch of lucky s.o.b's....i took my cat and muffler off my stock exhaust...threw a code...when i got my 5" i installed the finger stick and blocker plate...just my luck i guess...
 

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AKDZL;1578809; said:
Well how do you know you have a emission truck.. Yes a cali or federal, but is there any other way? I got mine out of Seattle, which came from Ohio at an auction. I am planing on getting an exhaust, (not sure which one yet, maybe Banks) and if I throw a code I have no way to reprogram it.

I'm from Ohio and live near Seattle now. I bought my truck out west here. I don't think my truck is an emissions hog???? Anyway, if the truck came from Ohio, it is most certainly not a emisions truck. They don't believe in that stuff back there. I think the new flash in the computer would fix that problem anyway.

Just got my cat cut off yesterday. I still have the stock exhaust, yes i'm cheap.......but it works. No codes and I drove the s*^t out of it yesterday to see if it was gowing to throw it and I got nothing. Only time will tell.
 

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I'm not sure, do I need to keep my Kat in Tucson?
 

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Took mine off three weeks ago. Love it so far. Seems no different than stock except for you here the turbo more. On another note I drive the same mundane drive to work five days a week. I reset my DIC every now and than and watch the milage. I have been running 17.9 week after week for months. Catless......18.3 now! FE9 fingered and blocked....no codes.

Griz
 
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