Hi C4a0s,
What you need is an output mode of 1 and a polarity of 1. The polarity is voltage high when active and you want to supply 12v from the ECU which means the mode needs to be high side. Switch to battery or to ground is what the ECU does internally and not what you have wired the other end of the relay to.
The ECU outputs have a slight voltage pull-up internally when they are off, this is the voltage you will be measuring at the moment.
I should also mention that only Auxilliary Outputs 1, 2, 5, 6, 7, 8 can do high side driving. And as I said you should always wire up the relays to be switched to ground (permanently attached to ECU 12v when the ECU is on).