well after looking in the MCF Parts Client they only show one model range for this particular truck but it is almost exactly the same as the other F Series 3 wheeled models using the micro command system.

First i would make sure the battery charge is good
then when that is ok run the self diagnostic test
There should be a diagram pasted under the hood and it will have a diagram layout of the control panel components on it and on one side it will show you the self diagnostic chart and what each step does and the result.
If you need assistance in doing this let me know and i can tell you how to do it.
The onboard diagnostic will test all the functions and switches and also will test the contactors on the control panel.
I suspect you may have one either not working or the tips or plunger armature are worn.

Let me ask this also, what does the display show you when the steer cuts out?
Normally it will display a number for what the battery charge is from 0 to 9 but when it codes out that will change to a different number or letter when the error occurs.