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Thread: 12V switching source on the E38 ecm... try pin 51

  1. #1
    Junior Member T2000's Avatar
    Join Date
    Mar 2010

    Default 12V switching source on the E38 ecm... try pin 51

    Whilst tidying up my wiring I was looking for a +12v switch wire for my LPG relay... so I went back to a wiring diagram I found earlier this week.

    Pin 51 on the E38 is labelled as "Fuel CTL-Sec" and in the wiring diagrams I have seen it is used to switch a fuel pump relay.

    Pin 51 is not populated in any of the PCM harnesses that I have seen (All Holdens) so I thought I would check to see if it could be used. And after popping a wire and connector into the Pin 51 cavity of C1/J1... viola - switched 12v

    As expected the wire is cold with ign off or in acc but is hot when ign is on.

    Shared for your benefit and so that I know where to find the info if I suffer another "grey moment"

    Credit to LSXworks and the E38 COS tutorial for the images that I have re-purposed in the following illustration.

    Click image for larger version. 

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  2. #2
    Lifetime Member GMPX's Avatar
    Join Date
    Apr 2003


    It is used for systems that have a secondary fuel pump, I think you got lucky that it functions, there may be some calibrations where it is disabled.
    I no longer monitor the forum, please either post your question or create a support ticket.

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