2001 lb7 ECM Trouble ?

gearguts

New member
Jul 30, 2016
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Not sure what to check next. I tried Daves nologic lb7 tune a few months ago just too see what it was like. I had to run a script since some differences exist between versions and etc. I followed the instructions posted and it worked fine. I got a few errors that pertained to missing maps, ones I just don't have in my older operating system. Nothing serious I hoped. I downloaded the tune and tried it out, started fine and drove fine backing out of the driveway but once I accelerated I could tell something was wrong. The engine ran fine and made power but was really noisy, bad "detonation knock" noisy. I turned around and I reinstalled my previous tune. Here's where the problems start, It's like something remained in the ecm or some hard parts have been damaged. I now have an irritating idle lope that changes with coolant temperature and the detonation sound remains but is much less extreme, I have been driving it regularly as I try to figure this out. I have now exhausted all the available checks that I can do on the hard parts and I cannot find a problem. It seems the ecm might be at fault. Before I start wasting more time chasing this problem I thought I would ask you guys on the tuning forum that do this all the time if you have ever damaged an ecm or other parts doing something similar to this with an older or quite possibly the first version of the duramax ? I'm really running out of ideas... Thanks for any help
 

ironmax

chock full of goodies
Jul 6, 2010
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Col. Ohio
Have you tried to reload original tune again? What is your tuning procedure when flashing ecm? Lb7's can be finicky and may require fuses be pulled to certain electronics to cut down on "noise" over the data bus.
 

gearguts

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Jul 30, 2016
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Yeah I've tried the original. Same procedure as always with efi live, works every time without errors. That doesn't mean there aren't any i suppose.. A good friend with an expensive scanner checked everything he could and didn't find any problems, but did note that the injector pulse width was the likely culprit. It fluctuates up and down with the rhythm of the idle lope and apparently should be much more stable . Any thoughts on this ? I never data logged the truck when it was running fine, I guess that would help for reference in this case. Hind-site is 20/20 ....
 

dndj

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Apr 13, 2019
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From what you describe, I would be looking for a reman ECM with a clean 2001 stock tune, or find someone nearby who is willing to do a temporary swap for testing purposes.
 

gearguts

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Jul 30, 2016
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I'm going to try that. I think the hardest part will be finding one though... What about the ficm ? any suspicions that It could be responsible ? I'm not too clear on what it actually does other than create the higher voltage for the injectors and fire them.
 

gearguts

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Jul 30, 2016
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I have managed to get somewhere with this. I had my mechanic friend who owns the autocal give me the original copy of my stock ecm file that he had saved years ago. If i load the program on my ecm from the memory stick the idle lope goes away. If I open the file with my copy of efi live and save it, then load it into my ecm the idle lope comes back.. I think something is screwed up in my settings.
 

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