They're fed with 5.0 volts on one wire. There should be 0.2 volts on the ground wire, and there's mechanical stops in it to make the signal voltage on the middle wire go from approximately 0.5 to 4.5 volts. When something causes the signal voltage to go outside that acceptable range, that's what sets a diagnostic fault code.

Answered by caradiodoc (expert)
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