The 'loop' is just that ..nothing fancy ..it's wire.

It's purpose is to 'detect' the pulses from the (edit: positive coil) wire. No voltage is applied to the 'loop'.

I bet that you've created a short circuit. I shudder to think how much of your under dash and ignition wiring looms are now melted beyond repair.

Time to go to a different auto electrician, but it might be easier to get another loom from a wreck, or from a cheap second hand car.

You may have only cooked the one wire, but more likely it was un-fused, and you've either blown the common 'fusible link' (if later utes have this?), or you've blown an ignition fuse. Depending on how you ran your new wiring, will determine what might have got melted when it went white hot.