Whereabouts on the display are the two pin-sized holes? There should be one above the steering position indicator and then a larger indicator at the bottom on either side, one green for power on and one amber which is the service indicator...are those the two that are illuminated? Is the amber one flashing or is it solid? Has the fault ever occured when the tech is on site and if so, did they check the service indicators in the back on the various modules? Normally if the display is unable to give an error code, one or more modules in the back will have a flashing service indicator light which gives the error code.

If no error codes are available on any module then you have to follow the wiring schematic and test every connection, relay and switch that could be causing power loss. Most of us start with the distribution board on these as loose wires and poor connections cause a lot of issues. Hopefully someone else has had this exact issue before.