[shorod]

Since the P0641 indicates that 5V reference bus A is either higher or lower than expected, I think your guy should focus on the other codes to see which parts are on bus A, measure the bus voltage, then disconnect sensors on that bus one at a time to see if unplugging one of them allows the bus voltage to go back to the 5V specification. Assuming the bus voltage is low and he's able to identify one sensor that seems to be dragging it low, then that sensor is likely bad. Or, if it seems several sensors need to be unplugged to allow the voltage to get within range, then the driver circuit within the ECM may be the culprit.

-Rod