Ignition Coil and Ignition Power Transistor

Operation

When the ignition power transistor unit is switched ON by the signals from the engine control module, the primary current of the ignition coil will flow. When the ignition power transistor unit is switched OFF, the primary current flow is interrupted, and high Voltage is produced at the secondary coil.

When the engine control module switches OFF the power transistor within the unit, the battery Voltage within the unit is applied to the ignition power transistor unit, and the ignition power transistor unit is switched ON In addition, the power transistor unit is switched OFF when the engine control module switches ON the power transistor within the unit.





Inspection

Using Oscilloscope

1. Primary signal of ignition coil

(1) Run the engine at an idle revolution speed.
(2) Connect the probe to oscilloscope pick-up point 1 as shown in the circuit diagram, and check the primary signal of the ignition coil.





2. Control signal of ignition power transistor

(1) Connect the probe to oscilloscope pick-up point 2 as shown in the circuit diagram, and check the control signal of the ignition power transistor.








Harness Inspection

Component Inspection

Ignition Coil





(1) Measurement of the primary coil resistance. Measure the resistance of the positive (+) terminal and negative (-) terminal of the ignition coil.

Standard value: 0.72-0.88 K Ohms

(2) Measurement of the secondary coil resistance. Measure the resistance of the positive (+) terminal and the high-Voltage terminal.

Standard value: 10.89-13.31 K Ohms

Ignition Power Transistor





NOTE: An analog-type circuit tester should be used.

(1) Connect the negative (-) terminal of the 1.5V power supply to terminal 2 of the ignition power transistor; then check whether there is continuity between terminal 3 and terminal 2 when terminal 1 and the positive (+) terminal are connected and disconnected.

NOTE: Connect the negative (-) probe of the circuit tester to terminal 3.





(2) Replace the ignition power transistor if there is a malfunction.