Ignition Coil and Ignition Power Transistor

Ignition Coil And Power Transistor Circuit:

To test the Power Transistor, located on the intake manifold, using an analog type circuit tester proceed as follows.

Power Transistor:

1. Disconnect the power transistor connector.

Power Transistor Connector Identification:

POWER TRANSISTOR
1. Disconnect the power transistor connector.
2. Connect a power supply of 1.5v (one dry cell) between power transistor terminals 2 (-) and 3 (+).
3. Check for continuity between terminals 1 (+) and 2 (-).

Continuity
Should exist

4. Remove power from terminals 2 and 3.
5. Check for continuity between terminals 1 (+) and 2 (-).

Continuity
Should not exist


IGNITION COIL
1. Using an ohmmeter, check the resistance value between the ignition coil primary terminals 1 and 2.

Resistance value
0.9 - 1.2 ohms

2. Using an ohmmeter, check the resistance value between ignition coil primary terminal 1 and the secondary high voltage terminal.

Resistance value
20k - 29k ohms


If the Power Transistor or Ignition coil unit fails any of these tests, replace as needed.

Primary Ignition Coil Signal Pattern:

OSCILLOSCOPE TEST
1. Run engine at idle speed.
2. Connect the scope probe to power transistor connector terminal 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 terminal 3 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 ignition coil connector and turn the key to the ON position.

2. Using a voltmeter, check the voltage between ignition coil harness terminal 2 and ground.

Voltage:
System voltage.

3. Turn the ignition switch to the off position. Using an ohm meter, check for continuity between the power transistor harness terminal 2 and ground.

Continuity:
Should exist.

4. With the power transistor connector disconnected, turn the key to the START position.
5. Using a voltmeter, check the voltage between power transistor harness connector terminal 3 and ground.

Voltage:
2 - 6 VDC.

6. Turn the key to the ON position.
7. Using a voltmeter, check the voltage between ignition timing adjustment connector terminal and ground.

Voltage:
4.0 - 5.2 VDC.


If any of the previous tests produce unsatisfactory results, the harness will need to be repaired or replaced. Once repairs have been completed, road test the vehicle to confirm that the repair has corrected the problem.

If the same problem reoccurs, it is possible that there is an intermittent failure of the component or the ECU. Check for looseness at all harness junctions and test for an intermittent failure.