The ignition coil's secondary voltage output capabilities can exceed 40,000 volts. Avoid contact with the C3I/EI high voltage secondary components when the engine is running, or personal injury may result.
To avoid damage to the computer control module or other ignition system components, do not use electrical test equipment such as battery or AC-powered voltmeter, ohmmeter, etc. or any type of tester other than specified.
To properly diagnosis the ignition systems and their problems, it will be necessary to refer to the diagnostic charts in the fuel injection section.
When performing electrical tests on the system, use a high impedance multimeter or quality digital voltmeter (DVM). Use of a 12 volt test light is not recommended.
To prevent electrostatic discharge damage, when working with the computer control module, do not touch the connector pins or soldered components on the circuit board.
When handling a PROM, CAL-PAK or MEM-CAL, do not touch the component leads. Also, do not remove the integrated circuit from the carrier.
Never pierce a high tension lead or boot for any testing purpose; otherwise, future problems are guaranteed.
Do not allow extension cords for power tools or droplights to lie on, near or across any vehicle electrical wiring.
Leave new components and modules in the shipping package until ready to install them.
Ignition System CheckSee Figures 1 through 8
Check for diagnostic trouble codes. If any are found, refer to the appropriate chart in
Driveability & Emissions Controls
Turn the ignition switch
. Verify that the Service Engine Soon light is ON.
Check the following:
Throttle Position Sensor (TPS)-if over 2.5 volts, at closed throttle, check the TPS and circuit.
Engine Coolant Temperature (ECT) sensor-if not between 22-266°F (30-130°C), check the sensor and circuit.
Disengage all injector connectors and install injector test light (J-34730-2 or equivalent) in injector harness. The test light should be OFF.
Perform this test on one injector from each bank.
Connect spark checker, (J 26792 or equivalent), and check for spark while cranking. Check at least 2 wires.
If spark occurs, Connect the spark plug wires and check for fuel spray at the injector(s) while cranking.
If no spark occurs, check for battery voltage to the ignition system. If OK, substitute known good parts for possible faulty ignition parts. If not, refer to the wiring diagrams to track down loss of voltage.
Fig. Fig. 1: Ignition system diagnosis-3.0L engine
Fig. Fig. 2: Ignition system diagnosis-3.0L engine
Fig. Fig. 3: Ignition system diagnosis-3.0L engine
Fig. Fig. 4: Ignition system diagnosis-3.1L engine
Fig. Fig. 5: Ignition system diagnosis-3.1L engine
Fig. Fig. 6: Ignition system diagnosis-3.3L engine
Fig. Fig. 7: Ignition system diagnosis-3.3L engine
Fig. Fig. 8: Ignition system diagnosis-3.3L engine