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.

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