Oh! I figured it had to do with power consumption concerns. There's plenty of amperage from the EEC relay anyhow so couldn't I jumper your 12V to 12V_MR pin? I can't really see any benefits from adding another relay if I've got enough amperage stock? Then I could just leave pin 1 disconnected.mck1117 wrote: ↑Fri Jan 08, 2021 8:29 pmYou already have a main relay, it's labeled "EEC Power Relay" on the wiring diagram. The ECU doesn't need constant 12v - just switched 12v from the ignition switch (this one is pretty low power - maybe 100mA draw), and the 12V_MR pin, which is for higher power stuff on the ECU, to be powered by an external relay. The ECU switches the main relay on after starting up itself using whatever normal output you have configured for it.
Also, I'm having a stupid moment and can't figure out why you have four Zener diodes to four of the low-side switches. Could you humor my lack of understanding here?