The ignition system uses individual ignition coil/module assemblies for each cylinder. The Powertrain Control Module (PCM) controls the individual coils by transmitting timing pulses on the Ignition Control (IC) circuit of each ignition coil/module to enable a spark event. The PCM monitors each IC circuit for improper voltage levels. Each ignition coil/module has the following circuits: An ignition voltage circuit, a ground, an IC circuit, and a low reference circuit.
If a problem with the ignition is intermittent, inspect for the following:
Wiring broken inside the insulation
Poor connection between the male and female terminal at a connector
Poor terminal to wire connection. Some conditions which fall under this description are poor wire crimps, poor solder joints, crimping over the wire insulation rather than the wire itself, and corrosion in the wire to terminal contact area
Pierced or damaged insulation can allow moisture to enter the wiring causing corrosion. The conductor wire may corrode inside the insulation with little visible evidence. Look for swollen and stiff sections of wire in the suspect circuits
Wiring which has been pinched, cut, or worn through insulation may cause an intermittent open or short as the bare area touches other wiring or parts of the vehicle
Wiring that comes in contact with hot engine or exhaust components
If a fault is found, make the appropriate repairs.