Before beginning any diagnosis and testing procedures, visually inspect the components of the ignition system and check for the following:
Check the spark plug wires and boots for signs of poor insulation that could cause cross firing. Make sure the battery is fully charged and that all accessories are off during diagnosis and testing. Make sure the idle speed is within specification.
You will need a good quality digital volt-ohmmeter and a spark tester to check the ignition system. A spark tester resembles a spark plug without threads and the side electrode removed. Do not attempt to use a modified spark plug.
No Spark Test
If no spark can be found at any spark plug or coil, you must first determine if a cranking rpm signal is present from the Crankshaft Position Sensor (CPS). This can be accomplished in various ways:
Connect a scan tool and watch for a CPS signal as the engine is cranked.
If it has been determined that cranking rpm is present, proceed as follows:
- Disengage the 6-pin connector from the DIS module, then turn the ignition key ON and measure the voltage to ground at terminal A (the ignition switch circuit). If battery voltage is not present, check for a blown fuse or an open or shorted circuit.
- Disengage the 5-pin connector from the DIS module, then check the resistance of terminal E to ground. If resistance is above 200 ohms, there is an open in the circuit. If the resistance is below 200 ohms, the problem is a loose terminal or a faulty DIS module.
If it has been determined that no cranking rpm is present, proceed as follows:
- Disengage the 5-pin connector from the DIS module, then measure the resistance between terminals A and B of the CPS. Sensor resistance should be 700-900 ohms.
- If CPS and circuit resistance is less than specification, remove the sensor from the engine and check the resistance directly; check to see if the sensor is still magnetized and check the continuity of the sensor wiring. Replace a sensor that does not have the proper resistance and/or is demagnetized, or repair open/shorted wires.
- If CPS resistance was within specification, set the voltmeter to the AC volt scale and connect the meter probes to terminals A and B of the DIS 5-pin connector. Crank the engine and watch for voltage. If while cranking, the sensor is putting out less than 200 millivolts, replace the CPS.
- With the ignition key ON , check for voltage at terminal A of the DIS module 6-pin connector. If no voltage is present, check for a blown fuse or an open/short in the circuit wiring. If voltage is present, check for loose terminals; if loose terminals are not the problem, the DIS module is at fault.
Secondary Spark Test
When it is suspected that a spark plug may not be firing, the simplest test consists of a visual inspection as noted above. If no loose or damaged wires can be found, each coil-to-plug wire should be checked for spark.
- Twist the boot of the spark plug wire to loosen it, then carefully pull upwards and disconnect the wire from the plug.
- Connect the spark plug wire to Spark Tester tool SA9199Z or equivalent.
- Connect the spark tester to a suitable engine ground.
- Crank the engine and watch for a strong spark across the tester gap.
- If the spark is missing or weak, check the resistance of the coil-to-plug wire; it should be less than 12,000 ohms. Replace any wire with too high a resistance and repeat the test. If the wire resistance is good, but the spark is missing or weak, proceed to the DIS MODULE SPARK TEST.
- If no spark can be found for all of the wires, proceed to the NO SPARK TEST.