When you hard wire the lines, the fuse blows on an American Kymco bike. The ECM is the actual switch for the lines, not the hi/low button on your handlebars. When you flip to HI beam, the low beam becomes grounded. When you switch back to low, the hi beam becomes grounded. The hi and low beams have an additional ground at the bulb so power usually flows through the element and into that ground if you are using the ECM. If you remove the ECM, there is no longer a switch so, assuming you turn on the hi beam, the line from the low beam is powered by the ground it shares at the bulb and pulls additional power (same happens when you turn on the low beam, the hi beam because powered by the ground at the bulb)... increasing the amperage and blowing a fuse. Only when it goes through the ECM does the line actually get "switched" so power cannot travel down it. In theory, a diode would solve the problem and prevent the line from becoming a ground aka another route for the power to flow. I currently only have the low beam hardwired up so I can ride to work without blinding anyone.
BTW. When I installed LED headlights, they did not pull enough amperage to blow the fuse. Combined, it pulls about 2 amps now. The problem is, the hi beam and low beam are both powered regardless of which line/beam I try to use leaving me with only hi beams if both are hardwired.