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Home >> GMC >> 1990 >> Forward Control 3.9 L >> Repair and Diagnosis (Single Page) >> Engine Performance >> Theory and Operation >> Engine Controls - Theory & Operation >> Computerized Engine Controls (Diesel) >> Engine Speed Sensor
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Engine Speed Sensor

The engine speed sensor is a camshaft driven pick-up and is mounted at center, rear of engine. The sensor receives a 5-volt reference signal and allows the ECM to measure engine RPM by the number of times reference voltage is pulsed. The engine speed sensor pulses 4 times per revolution.