Ignition Coil: Testing and Inspection

Coil Removal:

1. With the ignition switch (OFF) disconnect the ignition coil electrical connectors.

Ignition Coil Connector:

Ignition Coil Schematic:

2. Measure the resistance between terminal 1 and terminal 15 of the ignition coils.

^ Resistance should be 0.45 ohms (+10%). Replace as necessary.

NOTE: Resistance cannot be measured between terminal 4 and 4a of the coils.

3. With the ignition (ON) test for voltage at terminal 3 of the ignition coil electrical connector.

^ Reading should be 12 volts. If not check circuit between terminal 3 of the ignition coil and terminal 15 of the ignition switch for open or short. Repair as necessary.

4. Test circuit between terminal 2 of the ignition coil electrical connector and ground.

^ Reading should be 0 ohms. If not check circuit for opens.

5. While cranking the engine test for pulsating ground signal at terminal 1 of the ignition coil electrical connector.

^ Reading should alternate between 0 and infinite ohms resistance to ground. If not check the circuits to the final output stages of the DME control unit. If the circuits are OK refer to Computers and Control Systems for testing the DME control unit.

CAUTION: Be sure to use a DVOM or other special tool suitable for this use. Do not use test lights with incandescent bulbs for testing computer controlled circuits, ECM damage may result.

Do-It-Yourself LED Test Light:

Shop Made LED Test Light: A simple test light may be constructed from normally available components.

6. Check coils for signs of hair line cracks, or burning. Replace as necessary.