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: custom tune questions


Doodle
09-02-2009, 09:16 PM
I think I'm going to go ahead and get a custom tune rather than a handheld programmer. After doing a lot of research I'll spend the same on a custom tune and keep my old pcm for what it costs for a good programmer. However, I have a few more questions. First off, if I keep my old pcm and tune a new one can you switch back and forth between the two without doing a crank relearn? I've been told you don't have to by the tuner but wanted to make sure. At first I wasn't going to keep my stock pcm but for $100 as might as well have it as a backup. Second, concern is with check engine lights. Say down the road I have a check engine light come on. I take it to the dealer and he scans it to look for codes. Does this reset anything? I've heard that people swap out pcm's to stock when they take it to the dealer for service because it may "reflash" the pcm and they will lose the programing. Another question is if you have a diagnositic code throw on the tuned pcm and then swap out for the stock pcm will it still throw the same code? And vice versa if you have the stock one in and swap the tuned will the trouble codes be the same? Lastly, I think I'll just do the 87 tune. I don't always have acess to 91 out where I live. I'm not looking to have a drag racer just something with more pep starting out any maybe pick up a 1-2 mpg if possible. Is this tune even worth doing?

GetSome8.1HD
09-02-2009, 09:40 PM
You shouldnt have to do a relearn. I didnt even after a CPS. If you swap out PCMs with a CEL light on it will not show up untill it reads it again if at all. If its a prob it will show up again so no worries. You can leave tuned PCM in as long as they dont reflash the PCM which is unlikey in most instances. As for octane I wouldnt run anything less than premium even before my tune. Thats helps keep it out of KR to a degree. As Im sure you know you can still pick up a significant amount of power with just an 87 tune. Ask SnowtogoGMC on here (Mike) as he has been working on his 87 tune and has got it down pat here recently with good luck. Just removing the TM on that will be a huge difference. Good luck bud :thumb: