Power Transistor & Ignition Coil

Ignition Coil And Power Transistor Circuit:

Note: To test the Power Transistor / Ignition Coil use an analog type circuit tester and proceed as follows:

COMPONENT TEST

Note: The circuit tester used in the following test procedures should be an analog type.

1. Disconnect the electrical connector to the Power Transistor.

Testing The Power Transistor:

2. Connect the positive lead of an ohmmeter to terminal # 3, and the negative lead of the ohmmeter to terminal # 8.
Continuity should NOT exist.
3. Connect the positive lead of a 1.5 volt battery to terminal # 7 and the negative lead of the battery to terminal # 3.
Continuity should exist, while the battery is connected.

Testing The Power Transistor:

4. Connect the positive lead of the ohmmeter to terminal # 3, and the negative lead of the ohmmeter to terminal # 1.
Continuity should NOT exist.
5. Connect the positive lead of a 1.5 volt battery to terminal # 2 and the negative lead of the battery to terminal # 3.
Continuity should exist, while the battery is connected.

Primary Ignition Coil Signal Pattern:

OSCILLOSCOPE TEST
1. Run engine at idle speed.
2. Connect the scope probe to pick-up point #1 shown in the system schematic diagram and compare the primary ignition coil signal to the pattern shown.

Power Transistor Control Signal Pattern:

3. Run engine at idle speed.
4. Connect the scope probe to pick-up point #2 shown in the system schematic diagram and compare the power transistor control signal to the pattern shown.
If scope patterns are not as depicted in images, continue with the rest of the test procedures before replacing the assembly.

HARNESS TEST
1. Disconnect the Power transistor and ignition coil connectors.
2. Measure the voltage between terminal 3 of the ignition coil connector and ground.
Voltage: Battery voltage

3. Measure the voltage between terminal 6 of the power transistor connector and ground.
Voltage: Battery voltage

4. Disconnect the Engine Control Module connector.
5. Using an ohmmeter, check for continuity between the Engine Control Module terminal 109 and the power transistor terminal 4.
Continuity: Should exist

6. Check for a short to ground at the Engine Control Module terminal 109 and the power transistor terminal 4.
Continuity: Should not exist

7. Check for continuity between the ignition coil terminal 1 and the power transistor terminal 1.
Continuity: Should exist

8. Check for continuity between the ignition coil terminal 2 and the power transistor terminal 8.
Continuity: Should exist

9. Check for a short to ground at the ignition coil terminals 1 and 2, and the power transistor terminals 1 and 8.
Continuity: Should not exist

10. Check for continuity between the power transistor terminal 3 and ground.
Continuity: Should exist

11. Reconnect the ECM connector.
12. Using a voltmeter, measure the control signal to the ignition power transistor, with the key in the START position, between terminal 2 and ground, and terminal 7 and ground.
Voltage: 0.5 - 4.0 volts

13. Measure the voltage between the ignition timing adjustment connector and ground, with the ignition switch in the ON position.
Voltage: 4.0 - 5.2 volts