Self-Test Output
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 1985 Ford Ranger, 1985 Ford RV Cutaway, 1985 Ford Pickup, 1985 Ford Econoline, and 1985 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
Part of the Self-Test connector, service codes are transmitted through the output in the form of timed pulses. These pulses are read as diagnostic codes.