Quickly, easily and economically test electronic fuel injection signals. Supplied with Noid Lights to check GM TBI, Tools PFI, For Ford TBI, GM PFI, Geo TBI and GM SCPI. Easy to use - just disconnect the wiring to the fuel injectors, install the Noid Light into the injector wiring harness and crank or start the engine. A flashing light indicates normal pulsing voltage. A steady light or no light indicates an electrical problem. Supplied with instructions in a durable, plastic molded storage case.