You have a shop manual?

wiring diagram?

12v test lamp?

Yank all the push-on ends off your ballast/ ignition and the ECU, and probe with a lamp and SEE WHAT'S HOT. Everything should be dead with the key off.

Then find out which wire (color) it is and trace back to the bulkhead. Yank that section of the bulkhead connector off, make sure it's still hot at the bulkhead--that will eliminate a "welded" harness short under the hood.

Next thin I'd do is yank apart the connector going to the column/ ignition switch, to see if it's in there.