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P0600 is a generic code that you would get using a generic code reader indicating a fault with the serial communication link. It doesn't necessarily indicate a bad PCM.
What is the truck doing? Was the PCM replaced and not programmed to the VIN?
If the powertrain (engine and transmission) is working as designed, then the PCM must be doing its job. You will need to plug in a Tech-II or equivalent scan tool to diagnose the serial communications link fault.