Self-Test Output (STO)
The STO is a circuit in the ECA which transmits service codes, in the form of timed pulses, to either a VOM or STAR tester hooked-up at SELF-TEST connector. These pulses are read as diagnostic codes.
The STO is a circuit in the ECA which transmits service codes, in the form of timed pulses, to either a VOM or STAR tester hooked-up at SELF-TEST connector. These pulses are read as diagnostic codes.