You have to pull out the drive fuse, the get some blocks and put under the front rails on each side of the mast channels and tilt the mast forward onto the blocks. This will elevate the wheels off the floor.
Once you do that remove the cover off of the logic box and locate the 'run-diagnostic' switch.
Move the switch to the diagnostic position and turn on the key switch, the power will come on and the truck will cycle the line contactor and the display LED should show the number 1.
There are several tests it will do in a preset order.
You will need the diagram showing these in the order expected and you will have to manually interact with each one to perform the test it is doing. Once the test passes it will advance to the next test, to perform. Now when you get to the part where it checks the contactors you will have to use the run-diag switch to cycle through the tests for those.
Once the tests are completed the LED on the display should show a dash.
If it does not pass a test it will not advance to the next one.
When i get to my info i will send you the diagnostic diagram, probably this evening. Usually it is stuck under the hood under the seat area, when you raise the hood it's right there, hard to miss unless it was removed or came off.

Thanks
Swoop223