well according to the possible causes you should check the inverters first
the alarm 5 relates to the pump inverter, not sure why the steering had anything to do with it , i looked in the steer inverter alarm codes and it did not show an alarm 5 with that description, there was no alarm 5 at all, it jumped from 4 to 6.
In any case i would just check all the inverters
then check the motors , either way the problem will be in one or the other.
If you have another truck (same model and system in it) with a known good inverter in it try swapping it out and see if problem goes away.