The electronic ignition system controls fuel combustion by providing a spark to ignite the compressed air/fuel mixture at the correct time. The PCM controls the spark advance of the ignition system in order to provide optimum engine performance, fuel economy, and control of exhaust emissions. The Electronic ignition system has the following advantages over a mechanical distributor ignition system:

The electronic ignition system does not use the conventional distributor and coil. The ignition system consists of the following components/circuits:

The Crankshaft Position (CKP) sensor is located in the lower right rear of the engine, behind the starter. The CKP sensor is a dual magneto resistive type sensor. This sensor is not speed dependent. The dual micro switches monitor both notches of the reluctor wheel for greater accuracy. The CKP sensor works in conjunction with a 24X reluctor wheel. The reluctor wheel is mounted on the rear of the crankshaft. The 24X reluctor wheel uses two different width notches that are 15 degrees apart. This Pulse Width Encoded pattern allows cylinder position identification within 90 degrees of crankshaft rotation. In some cases, cylinder identification can be located in 45 degrees of crankshaft rotation. This reluctor wheel also has dual track notches that are 180 degrees out of phase. The dual track design allows for quicker starts and accuracy.

The PCM also receives a 4X signal from the Crankshaft Position sensor. The PCM utilizes the 4X signal for the following:

The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM can determine when a particular cylinder is on either a firing or exhaust stroke by the 24X signal. The CMP sensor is to determine what stroke the engine is on. The system will attempt to synchronize and look for an increase in the MAF signal. An increase in the MAF signal indicates the engine has started. If the PCM does not detect an increase in the MAF signal, a re-synchronize will occur to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.

The Camshaft Position (CMP) sensor is mounted through the top of the engine block at the rear of the valley cover. The CMP sensor works in conjunction with a 1X reluctor wheel. The reluctor wheel is located at the rear of the camshaft. The CMP sensor is used to determine whether a cylinder is on the firing or the exhaust stroke. As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The CMP sensor internal circuitry detects this and produces a signal which is used by the PCM. The PCM uses this signal in combination with the CKP 24X signal to determine crankshaft position and stroke.

The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM can determine when a particular cylinder is on either a firing or exhaust stroke by the 24X signal. The CMP sensor is used to determine what stroke the engine is on. The system will attempt to synchronize and look for an increase in the MAF signal. An increase in the MAF signal indicates the engine has started. If the PCM does not detect an increase in the MAF signal, a re-synchronize will occur to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.

The ignition system on this vehicle features a multiple coil configuration and is known as coil near plug. There are two styles of ignition coil assemblies (1, 2). The engine could have either style. The ignition coil mounting bracket is attached to the rocker cover (3). The secondary ignition wires are short compared to a distributor ignition system wire.

Eight ignition coils/modules are individually mounted above each cylinder on the rocker covers. The coils/modules are fired sequentially. There is an Ignition Control (IC) circuit for each ignition coil/module. The eight ignition control circuits are connected to the PCM. The PCM triggers each ignition coil/module individually and makes all timing decisions. The ignition coil/modules are supplied with the following circuits:

The ignition feed circuits are fused separately for each bank of the engine. The two fuses also supply the power for the injectors for that bank of the engine. Each coil/module is serviced separately.

This system puts out very high ignition energy for plug firing. Less energy is lost to ignition wire resistance because the ignition wires are shorter. Since the firing is sequential, each coil has seven events to saturate as opposed to the three in a waste spark arrangement. Futhermore, no energy is lost to the resistance of a waste spark system.

To properly control ignition timing, the PCM relies on the following information:

The Ignition Control (IC) system consists of the following components:

The Ignition Control utilizes the following to control spark timing functions:

There are important considerations to point out when servicing the ignition system. The following Noteworthy Information will list some of these to help the technician in servicing the ignition system.

The PCM is responsible for maintaining proper spark and fuel injection timing for all driving conditions. To provide optimum driveability and emissions, the PCM monitors input signals from the following components in calculating Ignition Control (IC) spark timing:

An Ignition control circuit that is open, grounded, or shorted to voltage sets an ignition control circuit DTC. If a fault occurs in the IC output circuit when the engine is running, the engine will experience a misfire. DTCs P0351-P0358 set when a malfunction is detected with an Ignition Control circuit. The PCM will disable the injector for the appropriate cylinder when an Ignition control DTC sets.

The PCM uses information from the engine coolant temperature sensor in addition to RPM to calculate spark advance values as follows:

High resistance in the engine coolant temperature sensor circuit could cause detonation. Low resistance in the engine coolant temperature sensor circuit could cause poor performance.

Engine Cranks But Will Not Run diagnostic table must be used to determine if the failure is in the ignition system or the fuel system if the engine cranks but will not run or immediately stalls. If DTC P0300, P0341, P0342, P0343, P0335, P0336 is set, the appropriate diagnostic trouble code table must be used for diagnosis.