The procedure differs if you have a manual or an automatic.
For a manual transmission (attach probes to back side of plug while plug is connected, ignition ON, engine not started, throttle closed): Positive probe to terminal A, negative to B. The voltage should be approximately 5 volts. Make a note of exact voltage. Now move positive probe to terminal C. The voltage should be 16 percent of the first reading.
For an automatic, take the reading from the square plug, not the flat plug. Connect Positive lead to Terminal A, and negative to D. Voltage should be approximately 5 volts. Write down exact reading. Now move positive lead to terminal B. The voltage here should be 82% of the first reading.