ECM Function

The ECM supplies either 5 or 12 volts to power various sensors or switches. The power is supplied through resistances in the ECM which are so high in value that a test light will not light when connected to the circuit. In some cases, even an ordinary shop voltmeter will not give an accurate reading because its resistance is too low. Therefore, a digital voltmeter with at least 10 megohms input impedance is required to ensure accurate voltage readings. Tool J 39200 meets this requirement. The ECM controls output circuits such as the injectors, fan relays, etc., by controlling The ground or the power feed circuit through transistors or through either of the following two devices:

• Output Driver Module (ODM)
• Quad Driver Module (QDM)

Fig 1: Identifying Quad Driver Module (QDM)

Courtesy of ISUZU MOTOR CO.