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Thread: LM1 offset voltages - some additional understanding needed

  1. #1
    Tuner in Training
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    Dec 2007
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    Horicon, WI
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    Question LM1 offset voltages - some additional understanding needed

    After quite a bit of reading and studying of the how-to's on this, I went through the voltage off-set adjustment procedure. As near as I can tell, I did everything as prescribed. At first, I came up with an adjustment of over 3.3 to get the histogram to average out at 14.7! See attached picture.

    So, I turned off the LM-1, powered it back on and tried it again. That time I came up with 9.85 which seems more reasonable.

    My question is: When I change the LM-1 graph back to 0 to 5 volts, shoudln't the AFR histogram show what the LM1 is reading now? Mine still reads 14.7.

    WB-O2 sensor is sitting in open air.

    Thanks for any help,
    Last edited by Braemerz28; 03-22-2008 at 12:47 PM.
    Scott Braemer
    2000 NHRA Trans Am - LS1
    2006 Trailblazer SS - LS2
    2008 GMC Sierra Denali - L92

  2. #2
    Advanced Tuner
    Join Date
    Jul 2006
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    218
    I just did this for my lc-1 and my ground off set was olny .3. I would start over with a free air cal and see what you get. If you had a lc1 i would have told you to check your grounds. I dont believe the lm1 has the same grounding issues as the lc1.

  3. #3
    Advanced Tuner
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    DFW Texas
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    did you click the calibrate button after you changed it back to 0-5v? not trying to insult you just start with simple and work your way up.

  4. #4
    Tuner in Training
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    Not insulted at all. I appreciate the response.

    After further work, I found two issues...

    1. I had the 10-18 PID loaded into the table AND I had the LM-1 PID that HPT comes with loaded in the table. So, I was getting an average of the two in my histogram. Trying to correct this average was causing the large offset issue.

    2. The LM-1 that I'm borrowing apparently needs to be cycled on and off in order to get it to recognize that it is now plugged into the serial port. So, I was making changes in the LM software and hitting the save button - which looked fine on the computer sreen, but wasn't making its way into the LM-1 control box all the time.

    So, after all of that mess, I ended up with a 0.065 voltage offset. Not too bad!!!

    Thanks for the help guys,
    Scott Braemer
    2000 NHRA Trans Am - LS1
    2006 Trailblazer SS - LS2
    2008 GMC Sierra Denali - L92