Gilera 633721 Workshop Manual page 288

Injection
14 - Check the earth insulation.
5 - 23 >1 MΩ (infinite)
YES go to 16 NO go to 15
15 - Repair or replace the cable harness.
16 - Connect the remote control switch and check
for battery voltage between terminals 5 and 23 with
the key switch in position "ON".
5 - 23 = Battery voltage with panel in position "ON"
YES go to 17
17 - Repeat the check with the electronic control unit connected and the engine cold.
5 - 23 = Battery voltage with panel in position "ON"
If the fault continues, replace the electronic control unit.
INJEC - 288
Nexus 500 euro 3