e38 bench harness question

[kipps]

I'm assembling a bench harness for my e38 ECM. I'd like to incorporate a LED to indicate when the ECM is powered on. It would be simple to just wire the LED into the power switch, but I'd rather if the LED actually indicated the power status of the ECM. This way, the LED would go out if the ECM got bricked or unplugged.

What could I pin the LED to in the e38 ECM, that would hold continuous power for as long as the ECM is powered up? The powertrain relay wire is tempting, but I suspect that might go off after a few minutes of inactivity. I could also potentially use one of the 5v reference wires, but I'm afraid those might also cut off after a short period of no crank signal.

Any suggestions?

[kipps]

Looking over the e38 pinouts, the "check engine" lamp caught my eye. Will this lamp stay illuminated the whole time the ignition is on but the engine is not running?

[2xLS1]

Been using bench harnesses for 17 years (P01, P59, E40, E38, T42, T43) and the only LED I have ever used is incorporated in the ignition power switch. IMO you are overthinking what you need.

[kipps]

Been using bench harnesses for 17 years (P01, P59, E40, E38, T42, T43) and the only LED I have ever used is incorporated in the ignition power switch. IMO you are overthinking what you need.

Yeah, I probably am. I was just hoping I could pull a ground wire from the e38 connector, and connect a LED through that.

I ordered the parts needed to make the bench harness. I've got a couple LED indicators coming. I'll likely wire up one on the ignition power switch like you said. I'll probably also wire one through the powertrain relay pin, just to see what it does. I'm intending to use the powertrain relay in it's stock configuration with my LS swap, so it will be a good chance to learn whether that relay behaves like I think it will or not.