https://mobilicab.com/F4hxm7zhX073ec...Carryall-2.pdf
Your diagram will be on page 306 under Electrical System, Electric Vehicles.
The Circuit Breaker gives power to the Tow/Run circuit, that gets power from the hot side of the solenoid via Pink wire, but that goes through a welded splice on the way to the circuit breaker. If you have full pack voltage on the small pink wire at the solenoid, but only 4v at the breaker, then follow the wiring and find the splice connection between them. It's common for those to corrode and cause poor connection/ low voltage.