Glad you fixed it!

The PATS system was a secondary symptom.

For everyone fixated on the keys and the PATS system, one major clue was given but was overlooked, the dashes in the odometer. That symptom means the PCM and the cluster did not power up together which will, 100% of the time, cause PATS to fail (but it is NOT a PATS problem). The most common reason is the PCM doesn't power up, often due to the PCM power relay failing. In this instance, it appears to be the issue that the relay could not energize or the PCM could not power up due to a missing ground.

Keep that "dashes in the odometer" observation in mind, ask if you have to, whenever anyone asks about apparent PATS issues on these trucks.

 

Thank you, I think your explanation hit the nail on the head, this was totally my screw up in not thinking things through and missing the tree for the forest.

Maybe others can learn from my inattention and not waste time or money going down rabbit holes before they recheck the basics.