I have sent you all the circuit diagram need for the mechanic to trouble shoot the circuit , there is a fusible link on the inner fender needs checking
and also all the grounds , the pcm connector inspected for any backed out pins making poor connection and als pcm location
most like if the battery & alternator and grounds and pcm connector is good & wiring , for the year of the truck, it will the pcm that control the charging rate is bad internally causing the no charge condition
The Power Train Control Module (PCM), is located in the engine compartment, on the left inner fender behind the left headlight assembly.
The dark green wire goes to the PCM (computer ) & Dark brown wire goes to the pcm , he need to follow these wires and od a continuity test
if wires are good replace PCM .
The main components of the alternator are the rotor, stator, rectifier, end shields and drive pulley. Direct current is available at the output "B+" terminal. Alternator output is controlled by voltage regulator circuitry contained within the power and logic modules of the Engine Controller.
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ASE Certified Technician