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 circuits consist of an engine control module (ECM) supplied 5-volt reference circuit, low reference circuit and an output signal circuit. The CKP sensor is an internally magnetic biased digital output integrated circuit sensing device. The sensor detects magnetic flux changes of the teeth and slots of a 58-tooth reluctor wheel on the crankshaft. Each tooth on the reluctor wheel is spaced at 60-tooth spacing, with 2 missing teeth for the reference gap. The CKP sensor produces an ON/OFF DC voltage of varying frequency, with 58 output pulses per crankshaft revolution. The frequency of the CKP sensor output depends on the velocity of the crankshaft. The CKP sensor sends a digital signal, which represents an image of the crankshaft reluctor wheel, to the ECM as each tooth on the wheel rotates past the CKP sensor. The ECM uses each CKP signal pulse to determine crankshaft speed and decodes the crankshaft reluctor wheel reference gap to identify crankshaft position. This information is then used to determine the optimum ignition and injection points of the engine. The ECM also uses CKP sensor output information to determine the camshaft relative position to the crankshaft, to control camshaft phasing, and to detect cylinder misfire.

The crankshaft reluctor wheel is part of the crankshaft. The reluctor wheel contains a pattern around the circumference of the wheel consisting of 58 teeth and a reference gap. Each tooth on the reluctor wheel is spaced at 60 tooth spacing, or 6 degrees apart from each other with 2 missing teeth for the reference gap. The engine control module (ECM) uses the teeth and reference gap to determine the crankshaft position (CKP) and speed.

The camshaft position (CMP) sensor is a 3-wire sensor that provides a digital output signal. The wire circuits consist of an engine control module (ECM) supplied 5-volt reference circuit, a low reference circuit between the CMP sensor and the ECM, and an output signal circuit from the CMP sensor to the ECM. The CMP sensor detects magnetic flux changes between the teeth and slots on the 4-tooth reluctor wheel. The CMP sensor provides a digital ON/OFF DC voltage of varying frequency with 4 varying width output pulses per each camshaft revolution. The frequency of the CMP sensor output signal depends on the speed of the camshaft. The ECM will recognize the narrow and wide tooth patterns to identify camshaft position, or which cylinder is in compression and which is in exhaust. The information is then used to determine the correct time and sequence for fuel injection and ignition spark events. The ECM also uses the CMP sensor output signal to determine the camshaft relative position to the crankshaft position.

The camshaft reluctor wheel is part of the camshaft. The wheel contains a pattern around the circumference, consisting of 2 narrow teeth and 2 wide teeth. The 4 falling/trailing edges of all 4 teeth are evenly spaced 90 degrees apart. The engine control module (ECM) decodes the narrow and wide tooth pattern to identify camshaft position.

The knock sensor (KS) system 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.

The 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 of the engine. The control module receives the KS signal through two signal circuits. 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 compression/power 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 condition. 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.

This ignition system consists of one ignition module combined with three separate ignition coils, assembled into one component. Between the engine control module (ECM) and the ignition module there are three separate ignition coil control circuits and a ground circuit. Power for the ignition module and the ignition primary coils is supplied by a fuse ignition circuit from the underhood fuse block. A separate ground wire is provided from the ignition module to the engine block. The ignition coil 1 control circuit controls the spark energy for cylinders 1 and 4. The ignition coil 2 circuit controls the spark energy for cylinders 2 and 5. The ignition coil 3 circuit controls the spark energy for cylinders 3 and 6. The ignition control module contains a solid state driver circuit for each separate coil. The ignition module driver will allow current to flow through the primary winding when a signal is received from the ECM. The ECM will control the amount of time or dwell that current is flowing through the primary coil windings. When the ECM commands the ignition coil control circuit OFF, this will interrupt current flow through the primary coil windings. When the ECM commands the ignition coil control circuit OFF, this will interrupt current flow through the primary coil windings. When current is interrupted to the primary windings, the ignition coil primary energy collapses across the secondary coil windings. This stepped up secondary energy will transfer to both spark plugs electrodes, by the spark plug wires attached to each end of the secondary coil winding. The primary windings of each coil are current limited to prevent overloading if the ignition coil control circuit is held ON for an extended time.

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: