Hello, I am sorry for the delay, Let me try my best to explain, I realize the alt tested ok but,, it is possible for the alt test to pass if? the problem is not happening right at the time of the test, One can not rule out the alternator however, this sysetm is PCM controlled, The PCM is what controls alternator regulating voltage, WE have seen alternators as well as PCM problems, Inside the PCM is circuitry that controls the charging, We do not have live data from a full scanner viewing the PCM controls for the alternator so,, I can only say it is going to be the alternator or the PCM, In the shop we actually see the PCM as the cause of your symptoms more than alternators, A shop can view data and help confirm one or the oher but without I can only supply information as to the possibles, Unsure what direction to send you, You can try the alternator and yo run say a 50/50 or a shop can help zero in on the problem area with full scanner, I would hate to see you run out and change the PCM, If you have the alt tested when the problem is happening as well as possible bench ttest this could help narrow down, Below is a by the book description
he charging system is turned on and off with the ignition switch. The system is on when the engine is running and the ASD relay is energized. The ASD relay is energized when the PCM grounds the ASD control circuit. This voltage is connected through the PCM or IPM (intelligent power module) (if equipped) and supplied to one of the generator field terminals (Gen. Source +) at the back of the generator.
The generator is driven by the engine through a serpentine belt and pulley or decoupler pulley arrangement.
The amount of DC current produced by the generator is controlled by the EVR (field control) circuitry contained within the PCM. This circuitry is connected in series with the second rotor field terminal and ground.