Astro Pneumatic 7898 Deluxe Noid Lite and GM AC Signal Test Lights Set. The most economic way to check electronic fuel injection (EFI) signals. Quickly and easily checks for systems of GM TBI, Bosch PFI Ford TBI, GM PFI, Geo TBI and GM SCPI. To test, just disconnect the fuel injectors, plug the Noid Lite into injector wiring harness then crank the engine. Normal voltage is indicated by flashing light which is visible from passenger compartment. Blow molded case for easy storage and transport.