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Thread: L92 swap help needed

  1. #1
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    Default L92 swap help needed

    I am in the process of swapping an E38 w/ T43 (6L80E) into a 99 Silverado.
    Truck is running alright, went out for first test drives.
    To be able to use the existing cluster we left the original ECM in the truck and wired
    the needed signals into it.
    The following issues are remaining:
    - MIL circuit - probably due to both ECMs wired to the same MIL lamp
    - Charging system - need to wire "generator turn on signal" to old ECM
    - OBD connector: wired both ECMs into the same OBD connector. EFILive will however not let me connect to the E38 if signals for the LS1B are present
    - VSS - due to the lack of an external VSS sensor on the 6L80E I have not figured out how to get the VSS signal into the LS1B ECM.
    Tried to wire the E38 C1, pin 57 into the VSS input but the speedo is not moving.
    I there any other way to get this to work? Do I need to change the calibration?
    We really want this to work as the VSS signal is also needed for the ABS system...
    I hope there is a way other than adding an VSS sensor and reluctor somewhere to the driveshaft.

    Currently we always need to disconnect the battery and then start to be able to get the Tranny to shift. If the ignition is cycled the transmission will not shift right...I know this sounds a little odd, but this is what we have observed. There are no DTCs from the transmission.
    2005 RCSB 2500HD GMC Sierra DURAMAX LLY
    1955 Chevy Truck 1st series, being restored
    2002 Mercedes C270 CDI

  2. #2
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    While having never done what you are working on, I'll speculate a bit.

    Since the MIL is most significant for the ECU controlling the engine, I would wire it to the E38. I suppose you could put another bulb somewhere for the LS1 PCM.

    I'm not sure what the logic is with the generator turn ON signal, but it probably has something to do with the engine running. The LS1 PCM won't know the engine is running without a 24x crank signal, so you'll have to use the E38 for alternator control.

    I think you'll need two OBDII connectors. I'm guessing the E38 will be more standalone and the LS1 PCM will be more specific to the truck and related truck modules.

    You may try using a Dakota Digital VSS module for more VSS options. You'll have to use the E38 VSS output to the Dakota Digital module and then use the Dakota Digital module's output(s) to satisfy other truck modules.

  3. #3
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    Thanks for the hint.
    I looked at what Dakota has to offer, are you referring to the SGI-5 - UNIVERSAL SIGNAL INTERFACE UNIT ?
    2005 RCSB 2500HD GMC Sierra DURAMAX LLY
    1955 Chevy Truck 1st series, being restored
    2002 Mercedes C270 CDI

  4. #4
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    Just wondering why keep the LS1 PCM ?? Can't the E38 handle the functions that you were keeping the
    old PCM for.

  5. #5
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    I was wondering the same thing, what on the old cluster doesnt work with the E38? If its the tach or speedo, you can adjust those in the E38. Fuel sender can be setup in the E38, temp gauge should be similar? If its the DIC options, that might be a reason but other than that Im not sure why you'd keep it.

    Are there BCM compatibility problems the E38 cant address?
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    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.

  6. #6
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    I believe S10Wildside is correct. A Gen IV swap into a Gen III truck will require both ECMs (PCM) to retain all of the truck’s original functionally. This will include 2 OBD-II ports and 2 MILs - one for each PCM / ECM.

    IPC (Instrument Panel Cluster) info:

    The 1999 Silverado IPC receives input in 3 ways - directly from a sensor, directly from the PCM, and via serial data (Class 2) communication.


    Inputs with a direct circuit to the IPC include:
    • oil pressure (gauge)
    • voltage (gauge)
    • turn signal indicator (light)
    • check engine oil press (message centre)

    • low washer fluid (message centre)
    Inputs the PCM sends directly to the IPC (non-serial data) include:
    • Speedometer
    • Tachometer

    • MIL or SES (light)
    All other inputs to the IPC are serial data (Class 2) - from the PCM / BCM / EBCM / SDM (ACM).

    The E38 does not use serial data communication. It uses GMLAN (CAN type) communication.

    Alternator Control

    Alternator Control in Gen IV trucks is often controlled by the BCM. In the E38 tune you will need to program the alternator control from “BCM” to “ECM”. I believe HPTuners has this functionality, EFILive does not as of yet. I sincerely hope this functionality is forthcoming in EFILive - it would be of great benefit to Gen IV conversions - similar to a VATS patch.

    VSS

    If you don’t want to add an aftermarket VSS sensor, you could try obtaining a VSS signal from the ABS sensor on one of the front wheel bearing assemblies. Your 1999 Silverado uses a 3 channel ABS system. Each front wheel has a dedicated ABS sensor. The rear wheel ABS use the VSS signal - originally on the transmission output shaft.


    Regards,
    Taz
    Last edited by Taz; May 1st, 2011 at 07:56 AM.

  7. #7
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    I'm assuming this project is already underway, but I would have simply changed the crank ring to a 24x.

  8. #8
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    Taz,

    you are right, there are a number of features sent via Class II data the E38 does not have.
    So far we have not hooked up the second BCM (2007 Escalade) but we have prepared the wiring for the alternator control (incl. current sensor)
    and we also plan to use it for tap up/down and cruise.
    Right now I am unclear about the resistor values for the cruise, there were more important things to do.....
    I figured that a speedo conversion box might also work, as we have one left over from a vehicle that does not need it any more.
    2005 RCSB 2500HD GMC Sierra DURAMAX LLY
    1955 Chevy Truck 1st series, being restored
    2002 Mercedes C270 CDI

  9. #9
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    Changing to 24x would have been an option, but VVT would be lost as well as the 6L80 !
    2005 RCSB 2500HD GMC Sierra DURAMAX LLY
    1955 Chevy Truck 1st series, being restored
    2002 Mercedes C270 CDI

  10. #10
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    Ah thanks for the sanity check Taz, an E67 would have been perfect for this because it has serial comms still (the reason the GMT360s use an E67 vs E38 so GM didnt have to rewire the entire truck). Keep VVT and 6L80E support too with the proper OS.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    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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