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 :cool:

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" :unsure::unsure::unsure:


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

Attachment 18113

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.