how can I trouble shoot the coil pack and the electric going to the coil pack. on 2003 Chevrolet Express 3500

Meaning how could I check the wiring harness.

Asked by for the 2003 Chevrolet Express 3500
No fire at all on any cylinder? If only one cyl. misfire, swap that coil with another one to see if misfire follows coil.
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check for spark
I have no spark I want to know how to check it back to a fuse