I could be wrong here but.

I believe the ecu is woken by the uch on pin D1 C connector, which the pulls the relay on K1 like you say, that then supplies power to the ecu.
Can you backprobe the K1 with ignition off, you should have a voltage through the relay solonoid. Last one I did was a faulty fuse box, if it's the one I'm thinking of that has the relays built in and are troublesome.

Also have you tried to supply an earth to that terminal to see if it switches the supply.