89 gt. I have 12v power at the computer ground quick disconnect. The computer is not in the car as it's being fixed. Why would I have 12v there with the key on
I would think some wire is making contact betweeen there and the computer. I would do a continuity check from that connector to each of the 60 pins of the computer harness and see which one is crossed. then you can trace out where the break is and repair or rewire.
There's a good youtube video from tecmotion (Matt) that go over how to test the 60 pin connector for shorts to ground, continuity etc.