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Thread: Truck uses Throttle Follower P/N Tables when In Gear

  1. #1
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    Default Truck uses Throttle Follower P/N Tables when In Gear

    Started messing with throttle follower yesterday. My PCM thinks it's in 1st gear all the time (according to GM.GEAR) with the 4L60E to T56 swap, even with the T56 segment swap from an f-body. Maybe it's because my clutch switch is not hooked into the PCM.

    Anyways, I zeroed out the throttle follower decay rate and decay delay in P/N (B4319 B4320). When I rev the engine the RPM's will hang at around 1300 RPM indefinitely when I'm parked. I did not try it when moving. So I put these tables back to stock and now it's back to normal. This tells me that the PCM is using the P/N throttle follower tables even though it claims to be in gear.

    Other P/N tables in the tune, like idle speed and idle airflow, are also zeroed out but it's correctly using the In Gear tables anyways.

    Anyone know what's going on here?

    Thanks!
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

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    Just spent some time in my log to see what the throttle follower was doing, and indeed it is using the P/N decay and delay tables even when moving and in 1st gear according to the GM.GEAR PID.

    But why isn't using the P/N tables anywhere else? Other P/N tables in the tune that are zeroed out are the idle speed, idle airflow, and throttle cracker.
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

  3. #3
    Joe (Moderator) joecar's Avatar
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    GM.GEAR is used by the AT, I don't believe it is used/updated for MT.

    MT determines gear by gear ratio (try logging GM.BOXRATIO).

    Both AT and MT use the P/N tables... for MT P/N means clutch is disengaged (detected via CPP switch).

    IDK why it's not using the other P/N tables (is your trans segment for AT or MT...?)

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    If the PCM is supposed to use the P/N idle speed table but it is zeroed out, will it perhaps default to the In Gear table instead?

    The trans segment is for a manual, I used an f-body manual segment and 12212156 OS.

    I will try logging GM.BOXRATIO
    Last edited by ferocity02; March 31st, 2013 at 09:50 AM.
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

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    I logged GM.BOXRATIO and it never left 0.0.

    Using the P/N throttle follower tables is not a problem, in fact I just spend a couple hours working on them. But it's concerning why it's using these P/N tables and no others...
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

  6. #6
    Joe (Moderator) joecar's Avatar
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    Looking back thru my logs looks like BOXRATIO and GEAR only work for AT.

    MT has no gear indicator at all.

    P/N works for both AT and MT as noted above.


    Do you have the CPP installed...?

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    Quote Originally Posted by joecar View Post
    Looking back thru my logs looks like BOXRATIO and GEAR only work for AT.

    MT has no gear indicator at all.

    P/N works for both AT and MT as noted above.


    Do you have the CPP installed...?
    I do have a clutch switch but it's not hooked to the PCM. It's only job is for allowing starting and to cut cruise control.

    If the P/N tables also work for a manual, why do the stock '02 Camaro and Corvette manual tunes have the P/N idle speed and idle desired airflow zeroed out?
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

  8. #8
    Joe (Moderator) joecar's Avatar
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    Good question, I don't know yet.

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    Im going to sound like a broken record here ferocity02, but why cant you just wire the CPP switch into the PCM? Im pretty sure most of the issues you're having are directly related to it not being connected to the PCM, sounds like you're getting frustrated so IMHO it'd be a LOT easier to just wire it up like GM had it and copy the values from a manual 4.8L tune to start with. You keep spending tons of time fighting it, why not make it easier on yourself?
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, starting the mods
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

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    Quote Originally Posted by ScarabEpic22 View Post
    Im going to sound like a broken record here ferocity02, but why cant you just wire the CPP switch into the PCM? Im pretty sure most of the issues you're having are directly related to it not being connected to the PCM, sounds like you're getting frustrated so IMHO it'd be a LOT easier to just wire it up like GM had it and copy the values from a manual 4.8L tune to start with. You keep spending tons of time fighting it, why not make it easier on yourself?
    Because it works well enough for me without the clutch switch hooked to the PCM, no need to add complexity to the tune either.

    The question here is if a manual tune does use P/N tables when the clutch is depressed or when it's in neutral, why are the idle P/N tables zeroed out in stock manual tunes? And why does it use the P/N throttle follower tables but no other P/N tables? My truck is clearly using the In Gear tables for some things, and the P/N tables for others. At this time, and without further understanding, I don't see how adding the clutch switch will help this.

    I also don't understand how the PCM knows when the trans is in neutral, other than the clutch being depressed, or if VSS is 0 and RPM is > 0.
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

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