Best way to find out wheres ground flows?

Hi guys,

I'm a Megasquirt user. I'm just saying since wiring diagram might be different.

I'm trying to understand what wire / circuit is causing MS to remains power On when ignition key is off.

I do have a DIY harness and using stock Ford Mustang harness (https://www.veryuseful.com/mustang/tech ... iagram.gif). Since I'm trying to isole things for another issue I do have, I've moved (bypass) MS Pin 28 (https://www.msextra.com/doc/pdf/html/MS3XV357_Hardware-1.5.pdf/MS3XV357_Hardware-1.5.html) straight to the battery with a switch.

I can start the car without MS switch On but battery voltage in TS doesnt make sense until I flip the MS switch On.

If I turn On ignition, MS will remains Off until I flip the switch On. It will reflect battery voltage: 12,6
If I turn MS switch Off while leaving ignition On, I do get 9,90v in TS ????

Is there a way I could place the DVOM to find out what is causing me that issue or where should I look at?


Thanks

I read elsewhere if Pin28 alone is moved to a different source, I will get strange behavior like this. That means for me this test is useless and will put back where it was.

Thank you for your time