No power when key turned on

[PugDad]

I disconnected the battery, and got under the truck to check all the connections at the starter.

I found the that the nut was loose enough that I could wiggle the connector. Not the 4 gauge main battery wire, but the 12 g wire that takes off there and goes up to the system.

Tightened it up, reconnected the battery, and re-checked the voltage at the terminal block on the firewall...before it was reading 9.xx volts, now it's reading the same as the battery, 12.xx.

Truck started up...happy day!