Reading Self-Test Codes: Notes
WARNING: This page is about a different car, the 1984 Ford Ranger, 1984 Ford Cab & Chassis, and 1984 Ford Bronco II. However, it is still accessible from the selected car via links, so may be relevant.
Service codes are transmitted to the Self-Test Output connector. They are shown as voltage pulses on a Volt-Ohmmeter (VOM), or as numbers on the STAR tester.