The electronic ignition (EI) system produces and controls the high energy secondary spark. This spark ignites the compressed air/fuel mixture at precisely the correct time, providing optimal performance, fuel economy, and control of exhaust emissions. The engine control module (ECM) primarily collects information from the crankshaft position (CKP) and camshaft position (CMP) sensors to control the sequence, dwell, and timing of the spark.

The crankshaft position (CKP) sensor is a hall-effect sensor. An integrated circuit (IC) magnetic sensing element inside the sensor is magnetically biased by a permanent magnet located within the sensor. The CKP sensor circuits consist of a 12-volt reference circuit, a low reference circuit, and a signal circuit. The CKP sensor produces a DC voltage of varying amplitude and frequency. The frequency depends on the velocity of the crankshaft and the DC output voltage depends on the 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 engine control module (ECM) processes the digital pulse to create a signature pattern that enables the ECM to determine the crankshaft position. The CMP sensor signal is used to determine the position of the valve train relative to 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.

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 reference gap is used to determine the crankshaft position (CKP), while the other teeth provide cylinder location during a revolution.

The camshaft position (CMP) sensor is a hall ignition control (IC) type sensor. The sensor is true power on (TPO) at power up, which means it is capable of recognizing whether it is in front of a tooth or a notch at power up, and to set its output accordingly. The sensor is a high technology product that integrates a self calibrating system that compensates for environmental changes, such as temperature and air gap. The sensor is composed of a magneto-electronic module that generates a magnetic signal and transforms it into a digital signal. The sensor operates in 2 functional modes. The first mode is the static functional mode. This mode is valid at sensor power up. In this mode, the sensor behaves like a simple DC hall IC switch with 2 fixed switching points. The static functional mode is active during the first 10 mechanical edges of the reluctor wheel and as long as the signal frequency is lower than 1.2 Hertz , plus or minus 0.5 Hertz , with the one tooth reluctor wheel. When the signal frequency exceeds the previous mentioned limit , the sensor switches to the second functional mode, the self-calibrating functional mode. This mode enables the sensor to reach high angular position accuracy , which is not possible to achieve in the static functional mode. In the self-calibrating mode, the sensor acts as a field induction sensor , which is more accurate at higher engine RPM. The sensor switches from self-calibrating mode to static functional mode when the signal frequency becomes lower than 0.3 Hertz, plus or minus 0.1 Hertz , with the 1-tooth reluctor wheel. When the sensor switches back from self-calibrating mode to the TPO mode, a pulse of short duration is generated on the sensor output signal. The pulse may occur on the low signal state or on the high signal state.

The CMP sensor wiring consists of a 12-volt reference circuit, a low reference circuit, and a signal circuit. The CMP sensors work in conjunction with a 1-tooth reluctor wheel on the exhaust CMP actuators. The CMP sensors work in conjunction with an 8-tooth reluctor wheel on the intake CMP actuators. As each tooth on the reluctor wheel passes the CMP sensor it sends a digital signal, which is an image of the wheel, to the engine control module (ECM). The ECM processes this information to determine the exact position of the camshafts, and to determine the optimum ignition and injection points of the engine.

The camshaft reluctor wheel is part of the camshaft position (CMP) actuator. This system consists of 2 different reluctor wheels. One for the exhaust camshafts on bank 1 and bank 2 and one for the intake camshafts on bank 1 and bank 2. The reluctor wheel on the exhaust CMP actuators has one tooth that extends 175 degrees around the circumference of the wheel. The reluctor wheel on the intake CMP actuators is an 8-tooth wheel that consists of 4 long and 4 short high and low phases. The 8X reluctor wheel is also used for the limp home mode.

Each ignition coil/module has the following circuits:

The engine control module (ECM) controls the individual coils by transmitting timing pulses on the IC circuit of each ignition coil/module to enable a 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 plug electrode is tipped with platinum for long wear and higher efficiency.

The knock sensor (KS) enables the control module to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The control module uses the KS system to test for abnormal engine noise that may indicate detonation, also known as spark knock.

This KS system uses one or 2 flat response 2-wire sensors. The sensor uses piezo-electric crystal technology that produces an AC voltage signal of varying amplitude and frequency based on the engine vibration or noise level. The amplitude and frequency are dependant upon the level of knock that the KS detects. The control module receives KS signal through a signal circuit. The KS ground is supplied by the control module through a low reference circuit.

The control module learns a minimum noise level, or background noise, at idle from the KS and uses calibrated values for the rest of the RPM range. The control module uses the minimum noise level to calculate a noise channel. A normal KS signal will ride within the noise channel. As engine speed and load change, the noise channel upper and lower parameters will change to accommodate the normal KS signal, keeping the signal within the channel. In order to determine which cylinders are knocking, the control module only uses KS signal information when each cylinder is near top dead center (TDC) of the firing stroke. If knock is present, the signal will range outside of the noise channel.

If the control module has determined that knock is present, it will retard the ignition timing to attempt to eliminate the knock. The control module will always try to work back to a zero compensation level, or no spark retard. An abnormal KS signal will stay outside of the noise channel or will not be present. KS diagnostics are calibrated to detect faults with the KS circuitry inside the control module, the KS wiring, or the KS voltage output. Some diagnostics are also calibrated to detect constant noise from an outside influence such as a loose/damaged component or excessive engine mechanical noise.

The engine control module (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:

During normal operation, the engine control module (ECM) controls all ignition functions. If either the crankshaft position (CKP) or the camshaft position (CMP) sensor signal is lost, the engine will continue to run because the ECM will default to a limp-home mode using the remaining sensor input. Each coil is internally protected against damage from excessive voltage. Diagnostic trouble codes are available to accurately diagnose the ignition system with a scan tool.