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Discussion Starter #1
Quick question for you all, I looked around but could not find an answer.

I'd like to install my Stainless Works headers, with high flow cats, in the next month. There are no provisions for rear O2 sensors currently on this set up. I was going to install some bungs but it seems easier to just turn them off.

My question is, when using HP Tuners, do I need an engine credit to turn off the rear O2 sensors? Or can I just hook up the tuner and do it? (and/or is there another way to do that?) I'm planning on getting the car tuned later this year but wanted to have the sensors turned off now so I can drive it without getting the permanent codes.
 

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Yes you will need credits to do an edit of the stock pcm. Without credits you can only monitor. Even with bungs you'd need the rears edited as more often than not high flow cats will still trip cat inefficiency codes. The other thing I'd recommend is to get it tuned as soon as you do the headers, as the headers will throw off the stock tune a bit.
 

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Any idea who will tune it later and what platform they use? If they use HPT anyway, you'll be spending the money for those credits at some point. Might as well do it now and not risk setting off permanent codes. It is a good idea to do a full tune at the same time, but the stock tune can compensate for the headers if they're installed correctly, you just won't be getting as much power out of them as you could be getting.
 

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Any idea who will tune it later and what platform they use? If they use HPT anyway, you'll be spending the money for those credits at some point. Might as well do it now and not risk setting off permanent codes. It is a good idea to do a full tune at the same time, but the stock tune can compensate for the headers if they're installed correctly, you just won't be getting as much power out of them as you could be getting.
Question...
Whats the big deal about setting permanent codes?
 

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Question...
Whats the big deal about setting permanent codes?
They can't be cleared, so you'll have a check engine light on. HPT, Livernois, etc can't clear those, nor can other OBD readers. They're only reset after the computer reads expected parameters on all sensors for an extended period (defined drive cycle as specified by GM). By turning off the rear sensors, the computer will never read the expected parameters, so you're stuck with the light. If you don't have OBD inspections and you're okay with the CEL, it's no big deal.
 

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They can't be cleared, so you'll have a check engine light on. HPT, Livernois, etc can't clear those, nor can other OBD readers. They're only reset after the computer reads expected parameters on all sensors for an extended period (defined drive cycle as specified by GM). By turning off the rear sensors, the computer will never read the expected parameters, so you're stuck with the light. If you don't have OBD inspections and you're okay with the CEL, it's no big deal.
Hmmm, I've been out of the "game" for a while but. Doesn't the CEL go out and a code remains when you clear with a scan tool, until you complete the drivecycle?? I get not wanting the readiness codes present if you must plug in for an inspection, but around here there is an visual too so it's a no go when your have missing O2's ect...
 

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Discussion Starter #7
Any idea who will tune it later and what platform they use? If they use HPT anyway, you'll be spending the money for those credits at some point. Might as well do it now and not risk setting off permanent codes. It is a good idea to do a full tune at the same time, but the stock tune can compensate for the headers if they're installed correctly, you just won't be getting as much power out of them as you could be getting.
The two tuners I have narrowed it down to both use HP so I'm good for that. I agree I should just tune it but I have a couple reasons why I can't right now. It's all good, it will be done soon enough :)
I've installed a few of these headers so I should be good.
Thanks for your reply
 

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Discussion Starter #8
Yes you will need credits to do an edit of the stock pcm. Without credits you can only monitor. Even with bungs you'd need the rears edited as more often than not high flow cats will still trip cat inefficiency codes. The other thing I'd recommend is to get it tuned as soon as you do the headers, as the headers will throw off the stock tune a bit.
Thank you!
 

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The reason he asked about what tuner you would use is because if you pay for credits to tuner a today just to turn off the secondary o2 check and then you bring it to tuner b in a few months to do a real tune you will still have to repurchase the credits.
For instance if I use my HP tuners to edit my tune I can edit it as many times as I want from my device on those same credits. If I then bring it to a buddy and he uses his device he has to use another couple credits to tune it even though I already have tuned it. The credits are linked to the ECU and the device used
 

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Discussion Starter #11
The reason he asked about what tuner you would use is because if you pay for credits to tuner a today just to turn off the secondary o2 check and then you bring it to tuner b in a few months to do a real tune you will still have to repurchase the credits.
For instance if I use my HP tuners to edit my tune I can edit it as many times as I want from my device on those same credits. If I then bring it to a buddy and he uses his device he has to use another couple credits to tune it even though I already have tuned it. The credits are linked to the ECU and the device used
I'll be doing a remote tune on my own device so it should work out, thanks for your input.
 

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That is not how permanent codes work
How do they work? I've looked it up and all I can find is they are only reset by the PCM with a drive cycle complete. So if it isn't a hard code the scan tool will turn the light off, but the code still remains until the cycle is completed. No?
Can you link to some good info on it please?
 

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They can't be cleared, so you'll have a check engine light on. HPT, Livernois, etc can't clear those, nor can other OBD readers. They're only reset after the computer reads expected parameters on all sensors for an extended period (defined drive cycle as specified by GM). By turning off the rear sensors, the computer will never read the expected parameters, so you're stuck with the light. If you don't have OBD inspections and you're okay with the CEL, it's no big deal.
So... even after the tune (ignoring O2s) it will still see it as a hard code? So you can't erase the code, even though the tune has now told the PCM to ignore the O2s?? Doesn't make sense but is this a good description?
 

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So... even after the tune (ignoring O2s) it will still see it as a hard code? So you can't erase the code, even though the tune has now told the PCM to ignore the O2s?? Doesn't make sense but is this a good description?
That is correct according to HPT and Livernois. The computer is looking for the correct voltage from the rear O2, even after they're turned off. Since they're off, the computer will never read the correct voltage, leaving you in limbo with a CEL due to the two cat inefficiency codes. Off the top of my head, the two codes are P0420 and P0430 if you want to dig for more information.
 

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That is correct according to HPT and Livernois. The computer is looking for the correct voltage from the rear O2, even after they're turned off. Since they're off, the computer will never read the correct voltage, leaving you in limbo with a CEL due to the two cat inefficiency codes. Off the top of my head, the two codes are P0420 and P0430 if you want to dig for more information.
Not sure I am reading this right, I have a Shane Hinds tune, and he by default disables the rear O2 sensors. Most times people that get a tune remove the cats, or go with headers and no cats. With my tune I have never had a check engine light or any codes, and has been this way for one year, no codes. I have looked at the tune with HPTuners, and they are disabled.
 

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Not sure I am reading this right, I have a Shane Hinds tune, and he by default disables the rear O2 sensors. Most times people that get a tune remove the cats, or go with headers and no cats. With my tune I have never had a check engine light or any codes, and has been this way for one year, no codes. I have looked at the tune with HPTuners, and they are disabled.
I understood from what he said that if you run them without a tune for long enough, THEN they will trigger the permanent codes. If you got a tune at around the same time you did your exhaust mods, it may have precluded the situation.
 

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OK, wasn't clear. Defiantly need to get the tune when cats are removed. I got my tune but still have my stock cats for now.
 

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Discussion Starter #18
I understood from what he said that if you run them without a tune for long enough, THEN they will trigger the permanent codes. If you got a tune at around the same time you did your exhaust mods, it may have precluded the situation.
Correct. I don't want to drive it, without the O2 sensors turned off, and get stuck with a permanent code. I'm just airing on the side of "caution" my buddy drove his for two days before he got his tune and got the codes. Some people get away with no codes, which is nice.
 

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Correct. I don't want to drive it, without the O2 sensors turned off, and get stuck with a permanent code. I'm just airing on the side of "caution" my buddy drove his for two days before he got his tune and got the codes. Some people get away with no codes, which is nice.
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"They can't be cleared, so you'll have a check engine light on."
Absolute hogwash
There is nothing like a "permanent" code
All codes in the ECM can be cleared and reset with HP tuners
 
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