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

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

The crankshaft position (CKP) sensor (2) used on this engine is actually 2 sensors within a single housing. Each sensor has a separate power, ground, and signal circuit. The PCM supplies 12 volts to both sensors. The PCM provides the ground path, or sensor return circuit, from both sensors. These power and ground circuits are also connected to the CMP sensor. Two separate signal circuits connect the CKP sensor and the PCM.

The PCM can use 3 different modes of decoding the crankshaft position. During normal operation, the PCM performs an Angle Based calculation using both signals to determine the crankshaft position. The dual sensor allows the engine to run even if one signal is lost. If either signal is lost, the PCM switches to a Time Based method of calculating the crankshaft position. If the system is operating in Time A mode, the PCM is using only the signal from Sensor A. Time B indicates that the Sensor B signal is being used. If the lost signal is restored, the PCM will continue to operate in Time Based mode for the remainder of the current key cycle. The PCM will revert back to the Angle Based mode on the next start if the fault is no longer present. The scan tool can display the Crank Position Sensing Decode Mode. A problem with sensor A will set a DTC P0335. A problem with sensor B will set a DTC P0385.

The camshaft position (CMP) sensor signal, when combined with the CKP sensor signal, enables the PCM to determine exactly which cylinder is on a firing stroke. The PCM can then properly synchronize the ignition system, the fuel injectors and the knock control. The CMP sensor has a power, ground, and signal circuit. The PCM supplies 12 volts to the sensor. The PCM provides the ground path, or sensor return circuit, from the sensor. These power and ground circuits are also connected to the CKP sensor. If a problem is detected with the CMP circuit, a DTC P0340 will set.

The ignition system on this engine uses an individual ignition coil for each cylinder. An ignition coil assembly consisting of 3 coils and an ignition control module is located in the center of each cam cover. This arrangement allows the ignition coil to connect directly to the spark plug using only a boot. This eliminates the need for secondary ignition wires. There are separate ignition modules for Bank 1 and for Bank 2. Each module controls the 3 ignition coils for that bank of cylinders. The PCM controls the ignition module operation. There are 6 ignition control (IC) circuits, one per cylinder, that connect the PCM and the ignition modules. Each ignition module also has a power feed, a chassis ground circuit , and a Reference Low circuit. The PCM causes spark to occur by pulsing the IC circuit, which signals the ignition module to trigger the ignition coil and fire the spark plug. The sequencing and the timing are PCM controlled.

The ignition feed circuits are fused separately for each bank of the engine. The 2 fuses also supply the injectors for that bank of the engine.

This system puts out very high ignition energy for plug firing. Because there are no ignition wires, there is no energy loss due to ignition wire resistance. Also, since the firing is sequential, each coil has 5 events to saturate as opposed to the 2 in a waste spark arrangement. Futhermore, no energy is lost to the resistance of a waste spark system.

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

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

An ignition control circuit that is open, grounded, or short to voltage will set 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 P1351-P1366 indicate that a malfunction has been detected on an ignition control circuit.

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

Therefore, detonation could be caused by a high resistance in the engine coolant temperature sensor circuit. Poor performance could be caused by a low resistance in the engine coolant temperature sensor circuit.

If the engine cranks but will not run or immediately stalls, the 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.