Guzzi doesn't use the color yellow to go to frame for ground. They use yellow for the light circuit. If you look in Guzziology there is a very good section on all the pin connectors and where they go in the harness.
Edit: I just looked at a wiring diag that is for LM2, should be the same. It had one diag for a printed dash board and one for wire dash.
The 12 pin connector only wire yellow has 2 wires on one side and one wire on other plug. Pin #4
If you only have 1 wire on each side of connector, that is where it goes.
You should have some lights not working, either no park in front or no tail light in back.
