Adjustable Probes fit all Electronic Fuel Injection Systems. Versatile tool tests throttle body injectors, ported fuel injectors and sequential central port injectors. One-person operation. Attach tool to the car body or windshield with suction cup. View the Noid Light from the front seat while cranking the ignition. A flashing light indicates normal pulses. No light or constant light indicates a problem. Two probe adapters screw on to form larger diameter probes. 27790 Probe Adapter 27870 Bulb 27890 Wire Assembly *12V bulb will not work on diesels