Electronic Ignition (EI) System Diagnosis
CIRCUIT DESCRIPTIONThere are 2 separate ignition module assemblies, one for each bank of cylinders. Each assembly contains an Ignition Control (IC) module and 4 ignition coils. Each IC module consists of the following circuits:
^ The ignition 1 voltage
^ A ground
^ The IC timing low reference
^ The IC control circuits for cylinders 1-8
Each ignition coil connects directly to its spark plug via a short boot. The IC control circuits transmit timing pulses from the powertrain control (PCM) module to the IC modules, which trigger the coils to fire the plugs in the correct sequence. The PCM monitors each IC control circuit for improper voltage levels.
DIAGNOSTIC AIDS
When servicing the ignition system components, use the following recommended procedures:
^ If a boot remains attached to a coil or to a spark plug, twist the boot prior to removal.
^ Inspect the boot for a missing or damaged internal spring.
^ Do not re-install any component that has visible signs of damage.
^ Install the boots onto the coils until the boots are bottomed out. Then install the assembly onto the spark plugs. If this is not possible due to space limitations, start the boots onto the spark plugs and then install the coil assembly as straight down onto the plugs as possible.
^ Ensure that the boots are installed right side up.
^ Lift the module beauty cover at the end opposite the module in order to remove.
^ Repair a torn perimeter seal with room temperature vulcanizing (RTV) sealant.
^ Adhere to the torque specifications when installing the coil cassette to the cam cover and the ignition module to the coil cassette.
A suspected ignition system misfire may actually be a condition other than the secondary ignition system. Verify proper operation of the following items:
^ The fuel system
- Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2.
- Fuel Injector Coil Test.
^ Engine Mechanical
Test for base engine conditions that could produce an engine misfire. Refer to Symptoms - Engine -4.0L. Testing and Inspection
TEST DESCRIPTION
Steps 1-8:
Steps 9-17:
Steps 18-25:
The numbers below refer to the step numbers on the diagnostic table.
6. An ignition coil, boots, or spark plugs may misfire only when moisture is present. Although difficult to test on this engine, selectively wetting down parts of the system and monitoring for misfire may isolate an intermittent condition. If moisture is present in the spark plug/ignition coil cavity of the cam cover, inspect the perimeter seal for damage. Repair any tears in the perimeter seal with an RTV sealant.
7. The J 26792 Spark Tester (ST 125) places a higher load on the secondary ignition than a normal spark plug.
14. Use the correct adaptor harness when connecting the Ignition Module Tester. Using an adaptor harness for a different engine application will result in incorrect tool operation.
The green Power LED should come on any time the ignition module tester is connected and the ignition switch is in the run position. This LED indicates that J 43298 Ignition Module Tester is receiving adequate power and ground to perform the test. The Test button is used as an LED check for the 4 red LEDs. In order to use this function, connect the tool, turn the ignition switch to run, then momentarily press the Test button. All 4 red LEDs should come on brightly. Then crank the vehicle. If the 4 red LEDs flash, this confirms proper operation of the primary ignition system, including the PCM, the wiring, the connections, and the Ignition Control Module (ICM). The ignition module tester may get hot during actual testing. This is because the tester is attempting to simulate the load of the ignition coils primary windings.
If the LEDs flash, the module output drivers are operating. If one or more LEDs are inoperative, and no individual IC Circuit (351-358) Group, or IC Circuit Group (1359 and/or 1360) DTCs are set, replace the module.