The electronic ignition (EI) system is responsible for producing and controlling a high energy secondary spark. This spark is used to ignite the compressed air/fuel mixture at precisely the correct time. This provides optimal performance, fuel economy, and control of exhaust emissions. This ignition system uses one coil for each pair of cylinders. Each pair of cylinders that are at top dead center (TDC) at the same time are known as companion cylinders. The cylinder that is at TDC of the compression stroke is called the event cylinder. The cylinder that is at TDC of the exhaust stroke is called the waste cylinder. When the coil is triggered both companion cylinder spark plugs fire at the same time, completing a series circuit. Because the lower pressure inside the waste cylinder offers very little resistance, the event cylinder uses most of the available voltage to produce a very high energy spark. This is known as waste spark ignition. The EI system consists of the following components:

The CKP sensor is a permanent magnet generator, known as a variable reluctance sensor. The magnetic field of the sensor is altered by a crankshaft mounted reluctor wheel that has seven machined slots, six of which are equally spaced 60 degrees apart. The seventh slot is spaced 10 degrees after one of the 60 degree slots. The CKP sensor produces seven pulses for each revolution of the crankshaft. The pulse from the 10 degree slot is known as the sync pulse. The sync pulse is used to synchronize the coil firing sequence with the CKP.

The camshaft position (CMP) sensor signal is a digital ON/OFF pulse, output once per revolution of the camshaft. The CMP sensor does not directly affect the operation of the ignition system. The CMP sensor information is used by the powertrain control module (PCM) to determine the position of the valve train relative to the crankshaft. By monitoring the CMP and CKP signals the PCM can accurately time the operation of the fuel injectors. The CMP sensor is connected to the PCM by a 12-volt, low reference, and signal circuit.

Each ignition coil is responsible for supplying secondary energy to a pair of spark plugs. The ICM converts the CKP sensor AC voltage into a DC input to the PCM. The IC control signals output by the PCM are amplified by the ICM in order to fire each coil. The spark events are triggered by the ICM, but the module has no influence on spark timing. There are two ignition coil and ICM configurations that depend on engine type. The ignition coils and ICM are remotely mounted with conventional spark plug wires on the 2.2L engine.

The PCM controls all ignition system functions, and constantly corrects the spark timing. The PCM monitors information from various sensor inputs that include the following:

There is one normal mode of operation, with the spark under PCM control. If the CKP pulses are lost the engine will not run. The loss of a CMP signal may result in a longer crank time since the PCM cannot determine which stroke the pistons are on. DTCs are available to accurately diagnose the ignition system with a scan tool.