Thank's for the reply. There is no codes appearing on the display. The E40XM I am working on does not have the deluxe display dash with the touch pad. It's a 2001 model year without that option.
But this afternoon, I started looking at the series of micro switches on the hydraulic control levers. At a certain moment the hydraulics would start working for a few seconds. I sprayed WD-40 penetrating oil on the micro switches and everything went back to normal. They used the forklift for several hours since, and it's still working. Just hope it keeps up !