VESPA GTV 250 i.e. 2008 Service Station Manual page 178

Injection
With the control unit and the injector disconnected,
check the continuity of the Red-Yellow cable be-
tween pin 14 of the interface wiring and the injector
connector
Switch to «ON» and check that, with the injector
disconnected and the control unit connected, there
is a voltage present between the Black-Green ca-
ble of the injector connector and earth.
INJEC - 178
Vespa GTV 250 i.e.