The electronic ignition system is of the direct ignition system (DIS) type and is controlled by the powertrain control module (PCM). The electronic ignition system is composed of the following components:
The electronic ignition system provides the following benefits:
The electronic ignition system components cannot be disassembled or repaired. A component that is correctly diagnosed as faulty must be replaced as a complete unit.
The powertrain control module (PCM) uses reference pulses from the crankshaft position (CKP) sensor in order to determine the engine speed. The PCM cannot operate the ignition system or the fuel injectors without the engine speed signal from the CKP. The PCM controls the ignition timing by controlling the ignition coils.
Each ignition coil has a built-in ignition module that controls the current flow in the primary coil winding. When the current flow is interrupted, the electrical field around the primary coil collapses and a high voltage is induced in the secondary coil. The secondary coil voltage travels from the coil output terminal, through the spark plug boot, and across the spark plug gap to the engine block. As a fail-safe function the ignition control module sends an ignition confirmation signal back to the PCM whenever the primary field collapses.
The camshaft position (CMP) sensor input is used to detect an engine misfire. The PCM also uses the CMP sensor signal as an input for modifying the fuel injection timing and for modifying the ignition timing.
The PCM receives information on the engine status from various engine sensors and then selects the most appropriate ignition timing settings from within the PCM's programming. The following are the most important inputs for determining ignition timing requirements:
The crankshaft position (CKP) sensor is located in the front cover of the cylinder block near the crankshaft pulley. The CKP sensor produces an AC signal that increases in both frequency and amplitude as the engine speed increases. The CKP sensor signal is sent to the PCM in order to indicate the RPM and the crankshaft position. The PCM uses the CKP sensor signal along with the camshaft position (CMP) sensor signal for the following purposes:
The CKP sensor reluctor (3) has 34 teeth and is mounted on the crankshaft behind the timing chain cover and the crankshaft pulley. When the crankshaft rotates, the CKP sensor signal rotor teeth pass by the CKP sensor (2) causing a fluctuation in the sensors magnetic field. The fluctuation in the magnetic field induces a voltage in the CKP sensor circuitry that corresponds to every 10 degrees of crankshaft rotation. The reluctor has one wide tooth (1) that indicates top dead center (TDC) of the number 1 cylinder. With the information that the PCM receives from the CKP sensor, the PCM determines engine speed and crankshaft position.
The camshaft position (CMP) sensor is located in the cylinder head near the number 4 fuel injector. The CMP sensor is a signal generator that is composed of a magnet and a coil with an iron core. The PCM relies on the AC signal provided by the CMP sensor in order perform the following:
The CMP sensor signal rotor (2) is part of the intake camshaft (1) and has 3 teeth located on the outer circumference. When the CMP sensor signal rotor (2) rotates past the CMP sensor (3), electrical signals are generated. The AC signals that are generated by the CMP sensor are sent to the PCM.
The knock sensor (KS) (1) is located below the intake manifold (2), on the engine block between cylinder 2 and cylinder 3. The KS detects engine detonation and sends a signal to the PCM. The PCM uses the input from the KS to adjust the ignition timing in order to control detonation. For detailed information on the operation of the KS refer to Knock Sensor (KS) System Description .
Consider the following important information when servicing the ignition system:
