Ah, ok - thanks for the explanation. That makes sense now.
Now that I've got everything back together and the Relay control wired up to the Secondary Air Pump contact, it's behaving differently
.
That contact now gets power with the first click of the Ignition, and only turns off with Ignition fully off.
Sigh, makes me look like I was dreaming the other day, but I know I wasn't.
There's probably a lot more behind the ECM's control of that line, than a simple engine on/off. I thought it might be current-sensing (ie sensing if that line is open-circuit or not). But even with my contact removed again, it still got 12V with the first click of the Ignition. Even a warm start didn't change it. Might have something to do with the ECU reset that would've happened, because I had the battery disconnected....who knows what paramaters the ECU uses for that...
Anyway, probably nothing anyone can help with. 90% of the work is done, I'll just check the other relays and find another one.