No, you don't test the lanyard, you need to test the post in the ski itself.
Does the ski have a good battery installed...minimum 12.6/7/8 volts?
1) Nothing connected, no key ...press the SS button once...does the ski wake up and display anything on the infocenter guage
2) Install the key on the DESS post...the ski should beep twice at you. 2 beeps mean the ski/mpem recognizes the key. The MPEM has memory and once a key is programmed into its memory, that is A key that will be able to start the ski. NO OTHER key will work until the MPEM memory is updated with another key...I believe the MPEM can accomodate 8 keys in memory.
3) If the ski sounds one long beep, the MPEM doesn't recognize the key and the ski won't start. This is an anti-theft feature. Could be bad connection between key and post, wrong key, salt water in key, MPEM is bad or wiring harness connection to MPEM is not making good contact.
At this stage....I recommend that you go through all the electrical connections first.....wiggling them, disconnect and re-connect them, clean all electrical connections to bright and tight...check all connections for any corrosion......open up the electric boxes and check all ground connections.