The best thing to do is remove the output connection from the alternator ( red wire/cable) and to the battery and starter. Ohm the cable out point to point and check for any shorts to ground. Also, keep in mind those cables have fusible links that could open up.
From looking at the circuit also check the ALT SENSE fuse (10 amp) at the main engine compartment fuse box. At the alternator 4 pin connector this should be an orange wire so if the fuse is good check for voltage input. Only two of the four pins are used on the 4 pin connector. Pins D and B. Pin D is alternator sense and Pin B is the monitor output (Generator Terminal L Output) to the PCM module which should be a red wire. Pins A and C are not used.
The voltage parameters that the PCM monitors for is 11.2 v (low) to 16.5 v (hgh). If the voltage is too low or high the internal voltage regulator in the alternator causes a shunt condition at the field rotor windings of the alternator meaning no output.