I hate to be discouraging but I had a similar problem with a QD 7.5 and, as I remember it, the same code. The ECU was not seeing the correct voltage or frequency and shutting the engine down. A service center removed all the covers and found that a magnet had become "unbonded" and had damaged the stator, rotor, and the cooling fan fins. Chunks of the magnet were throughout the interior of the generator case. They replaced the rotor, stator, and cooling fan, which only took a day after getting the parts from Cummins. Fortunately, the electronics were not damaged but the repair was still $3,000. Before authorizing the repair, I spoke to the closest Cummins center and they said that they would replace the entire generator, not rebuild it, adding several thousand dollars more to the cost. The generator had less than 500 hours on it when the failure occurred. That was 5 years ago and it continues to perform well.