VESPA GTS Super 300 ie 2008 Service Station Manual page 202

Injection
With the control unit and the injector disconnected,
check the continuity of the Red-Yellow cable be-
tween pin 34 of the interface wiring and the injector
connector
Switch to «ON» and check if there is voltage, with
injector disconnected and control unit connected,
between the Black-Green cable of the injector con-
nector and the ground lead
INJEC - 202
Vespa GTS Super 300 ie (2008)