Technician Handbook ! 673 Electronic & Computer Controlled Systems Power-Side Control Most circuits in Toyota vehicles are ground-side controlled. When a pulse- width modulated circuit is power-side controlled, the voltage modulation is observable after the ECU and before the load. In this arrangement, the circuit is ON when the voltage rises. Note that if voltage is measured after the load, a very minute change in voltage occurs as the circuit is modulated. At this point in the circuit, voltage is zero when the circuit is open. When the circuit is closed, ground voltage is present. The difference is usually less than 0.1V and may not be observable depending on your scope settings.
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