A proven test device to quickly determine of the electrical signal is present at the fuel injector
This noid lite covers GM port fuel injection (PFI)
Noid-Lites are the fastest, easiest, most economical way to check electronic fuel injection signals. Simply disconnect the fuel injector, plug in the Noid-Lite, and crank the engine. Normal pulsing voltage is indicated by flashing light which is visible from the passenger compartment.