The Electronic Ignition (EI) System produces and controls 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 an ignition control module (ICM) for each bank. The ICM consist of a controller and ignition coils. The ICM are mounted in the center of each camshaft cover, with short boots connecting the coils to the spark plugs. The engine control module (ECM) primarily uses engine speed and position information from the crankshaft (CKP) and camshaft position (CMP) sensors to control the sequence, dwell, and timing of the spark.

The CMP sensor is a hall effect switching device used to determine the position of the bank 2 exhaust camshaft. The CMP sensor detects a single tooth on the reluctor wheel of the camshaft, which denotes 90 degrees before top-dead-center cylinder 1 compression stroke. The sensor is used by the ECM to determine when cylinder 1 is approaching top dead center, necessary to synchronize the correct firing order. The CMP sensor is also used to enable sequential or independent fuel injection, and to enable spark knock control.

As the reluctor wheel tooth rotates past the sensor, the sensors internal hall effect device pulls the signal circuit to ground. Therefore, the ECM expects to see one high, 12 volts, to low, 0 volts, voltage transition once every two crankshaft rotations as the reluctor tooth passes the sensor. The signal circuit should be at 12 volts at all times except when the transition occurs. If an error occurs in the CMP sensor circuit during the drive cycle, the ECM will continue to supply fuel and spark to the correct cylinder at the correct time until the ignition is turned OFF. If an error occurs in the CMP sensor circuit upon key-up, then the engine is started, the ECM will default to supplying spark to both mating cylinders and enter non-sequential fuel injection. The engine may experience a 2-3 second extended crank, however, the engine will start and run.

The crankshaft reluctor wheel is part of the crankshaft. The reluctor wheel consists of 58 teeth and a reference gap. Each tooth on the reluctor wheel is spaced 6 degrees apart with a 12-degree space for the reference gap. The pulse from the reference gap is known as the sync pulse. The sync pulse is used to synchronize the coil firing sequence with the crankshaft position, while the other teeth provide cylinder location during a revolution.

The reference gap enables the ECM to determine top-dead-center for cylinder 1 and its mating cylinder, cylinder 4.

The CKP sensor is a permanent magnet generator known as a variable reluctance sensor. The CKP sensor produces an AC voltage of varying amplitude and frequency. Frequency depends on the velocity of the crankshaft. AC voltage output depends on crankshaft position and battery voltage. The CKP sensor works in conjunction with a 58-tooth reluctor wheel attached to the crankshaft. As each reluctor wheel tooth rotates past the CKP sensor, the resulting change in the magnetic field is used by the sensor electronics to produce a digital output pulse. The sensor returns a digital ON/OFF pulse 58 times per crankshaft revolution. The ECM processes the pulses to create a signature pattern that enables the ECM to determine the crankshaft position. The ECM can synchronize the ignition timing, the fuel injector timing, and the spark knock control based on the CKP sensor and CMP sensor inputs. The CKP sensor is also used to detect misfire and tachometer display. The ECM learns the variations between all of the 58-teeth under different speed and load conditions to correctly detect misfires. The CKP sensor circuits consist of a CKP sensor high circuit and a CKP sensor low circuit. The two wires are twisted together and uses a pull-up voltage of 2.5 volts produced by the ECM to prevent electromagnetic interference on the CKP sensor circuits.

Each ICM has the following circuits:

The ECM can command each ignition coil ON by grounding the IC control circuit of the ignition coil. The IC control circuit is pulse width modulated ON/OFF in order to precisely control the spark event.

The spark plugs are connected to each coil by a short boot. The boot contains a spring that conducts the spark energy from the coil to the spark plug. The spark plugs are tipped with platinum for long wear and higher efficiency.

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

There is only one mode of operation that is the ECM always controls spark. If the CKP pulses are lost the engine will not run. The loss of the CMP signal may result in a longer crank time since the ECM can not determine which stroke the pistons are on.