Reset PCM, BLM=120?
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Pro
Joined: Jan 2005
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From: San Jose Ca
Reset PCM, BLM=120?
Everything that I've read indicates that the PCM should default to BLM=128 for all cells after a PCM reset until closed loop is achieved and actual values replace the default of 128. Well, not on my ride! My car is a '94 'vette, and have had it since new. Whenever I reset the PCM, it defaults to BLM=120, except at WOT, which is 128. It has ALWAYS done this. Normally this wouldn't be much of a problem, but now that I'm doing some serious tuning with LT1 edit, I'm of course shooting for 128. This makes open loop opperation a bit difficult as again, it defaults to 120, which is of course, leaner than 128. I don't know if this a Y body specific thing, or what as I've never heard the F body guys mentioning this. The only way I've found to get around this, especially when I'm running an open loop program (which is my final goal), is to get my old Tech 1 and perform a BLM reset opperation. After that, all cells are 128. But if I upload a new program (which esentially causes a PCM reset after programming), I'm back to 120 and serching for the Tech 1 again. Any ideas??? 
Instructor
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But if I upload a new program (which esentially causes a PCM reset after programming), I'm back to 120
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Joined: Jan 2005
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From: San Jose Ca
Originally Posted by Blower91
How do you upload a new program? Perhaps that program has a bug? Perhaps it will not reset BLM when "uploading", just copying old BLM data? Your Tech 1 is reseting the BLM properly, right?
Drifting
Joined: May 2003
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From: Charlotte NC
St. Jude Donor '05
Cars can make adjustments in open loop. Don't believe me? make a program that is reallly lean or really rich.. You'll see the data flash for a very brief second and it will pick a BLM closer to what it needs. It gets it closer when the o2s get really warm.
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From: San Jose Ca
Originally Posted by Alvin
Cars can make adjustments in open loop. Don't believe me? make a program that is reallly lean or really rich.. You'll see the data flash for a very brief second and it will pick a BLM closer to what it needs. It gets it closer when the o2s get really warm.
What you're probably seeing is the PCM applying what it learned in prior closed loop opperation to the appropriate BLM cell in open loop. I've seen this too, but it doesn't mean that it's activly applying correction, just what it learned previously.
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BTW, for those that are interested, I've discovered the reason for this problem of mine. With the help of another forum member, I found that there is a parameter for "Minimum BLM keep alive" and "Maximum BLM keep alive" that is only available in Tunercat. I loaded my Tunercat, with a more recent ecm definition file than I had previously been using, an lo and behold, they were set at 120 and 160 respectivly. I reviewed my bone stock file and it said 120 and 160 too. I checked a stock F body M6 file, and the settings were 128 and 160. So it seems that this is a quirk of the Y body program. I wonder why they did this?
Last edited by MaxLean; May 29, 2005 at 08:47 PM.
