Ignition Control System Tests
NOTE:
Ensure battery is fully charged before performing tests.
- Check Ignition System For Proper Spark
Remove spark plug wire cap from each spark plug. Install known-good spark plug to spark plug wire and position spark plug so it is grounded to engine. Crank engine. If spark does not occur at each spark plug, go to next step. If spark occurs at each spark plug, see FUEL PUMP CIRCUIT TESTS under FUEL SYSTEM. - Check Power Supply Circuit At Ignition Coil & Ignitor Assembly
Turn ignition off. Disconnect connector from ignition coil and ignitor assembly. Turn ignition on. Using a DVOM, measure voltage between ignition coil and ignitor assembly harness connector (ECM side) terminal No. 2 and ground. See Fig 1. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, repair open circuit in harness between ignition coil and ignitor assembly and ignition switch connector. Also check for poor contact in connectors between ignition coil and ignitor assembly and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. - Check Ignition Coil & Ignitor Assembly Ground Circuit
Turn ignition off. Disconnect connector from ignition coil and ignitor assembly. Measure resistance between ignition coil and ignitor assembly harness connector (ECM side) terminal No. 3 and ground. See Fig 1. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit in harness between coil and ignitor assembly and ground. See appropriate wiring diagram in WIRING DIAGRAMS article. - Check Ignition Coil & Ignitor Assembly
Measure primary resistance between ignition coil terminals. See IGNITION COIL RESISTANCE - OHMS @ 68°F (20°C) table under IGNITION COIL RESISTANCE. If resistance is not as specified, replace coil. If resistance is as specified, go to next step. - Measure secondary resistance. See IGNITION COIL RESISTANCE - OHMS @ 68°F (20°C) table under IGNITION COIL RESISTANCE. If resistance is not as specified, replace ignition coil.
- Check Ignition Coil & Ignitor Assembly Input Signal
Reconnect ignition coil and ignitor assembly connector. Check for voltage during cranking by individually backprobing between ignition coil and ignitor assembly connector terminals No. 1 and 4 and ground. Ensure input signal voltage fluctuates with engine speed while cranking. If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, replace ignition coil and ignitor assembly. - Check Harness Between ECM & Ignition Coil & Ignitor Assembly Connector
Turn ignition off. Disconnect ECM connector B134 (35-pin connector) from ECM. See Figure. Disconnect connector from ignition coil and ignitor assembly. Measure resistance of harness between ECM and ignition coil and ignitor assembly. See ECM & IGNITOR HARNESS TERMINAL IDENTIFICATION table. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, repair open in harness between ECM and ignition coil and ignitor assembly connector. Also check for poor contact in connectors between ignition coil and ignitor assembly and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article.ECM & IGNITOR HARNESS TERMINAL IDENTIFICATIONECM Connector B134 Terminal No. Ignition Coil & Ignitor Assembly Connector Terminal No. 25 1 26 4 - Individually measure resistance of harness between ECM connector B134 (35-pin connector) terminals No. 25 and 26 and ground. See Figure. Resistance should be more than one megohm minimum for both test points. If resistance is less than specified, repair short to ground in harness between ECM and ignition coil and ignitor assembly. See appropriate wiring diagram in WIRING DIAGRAMS article. If resistance is as specified, check for poor contact at ECM connector. If contact is okay, check fuel pump circuit. See FUEL PUMP CIRCUIT TESTS under FUEL SYSTEM.