So if you connect tester lead + to black/yellow, lead - to ground, key off, no power, then turn key to position 1, you read 12V? If so, then yes, connect the black/yellow to your unit's ignition switched power lead, which I assume is the red one.
Yellow is usually constant power to unit, so if the tester shows 12V at the red/white wire, key off, then yes connect this too.
Anyone else know what this mysterious black box is under the floormats?
