Single beep?
One single beep normally means that you are using the wrong lanyard. Have you recently started this ski with that lanyard?
You should be able to go into advanced diagnostics. Are you following the complete instructions? It's not un-common for someone to try the advanced diagnostics and forget to remove the lanyard.
You need to push the start/stop button, with the lanyard removed, 5 times. Then, you should hear one long, one short beep. Then, put the lanyard cap on. How many beeps did you hear. If none, then push the start button.
Outside the "hi temp" error message, does the ski turn over? When you connect the lanyard, does your gages come alive? I wouldn't worry about the error message until you get the correct beeps from the MPEM.:cheers: