You can take some resistance measurements, it's outlined in the service manual. I don't think it's a full test but it could help determine if the MPEM is good or bad. You also can take it to a dealer and have him check it with a buds system, gonna be big bucks.
What is the ski doing? Have you check the fuses and which fuse if any is blown? What happens when you replace the fuse? On your ski all the fuses are in the front E-Box, three I think. If the 5A fuse is blown it's probably the MPEM, check and post back.
Lou