Circuit Description

A Direct Ignition System (DIS) is used on this vehicle.

The DIS is a 1-cylinder ignition system in which each cylinder is ignited by one ignition coil and one spark plug is connected to the end of each secondary wiring. A powerful voltage, generated in the secondary wiring, is applied directly to each spark plug. The sparks of the spark plugs pass from the center electrodes to the ground electrodes.

The ECM determines the ignition timing and transmits the ignition (IGT) signals to each cylinder. Using the IGT signal, the ECM turns the power transistor inside the igniter on and off. The power transistor, in turn, switches on and off the current to the primary coil. When the current to the primary coil is cut off, a powerful voltage is generated in the secondary coil. This voltage is applied to the spark plugs, causing them to spark inside the cylinders. As the ECM cuts the current to the primary coil, the igniter sends back an ignition confirmation (IGF1) signal to the ECM, for each cylinder ignition.

Fig 1: Ignition Coil Primary/Secondary Circuit Diagram

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Reference: Inspection using an oscilloscope.

While cranking or idling, check the waveform between terminals IGT (1 to 4) and E1, and IGF1 and E1 of the E3 and E4 ECM connectors.

Fig 2: Checking Waveform Between Terminals IGT (1 To 4) & E1

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