For 1990-2009 cars

The electronic ignition (EI) system is responsible for producing and controlling a high energy secondary spark. This spark is used to ignite the compressed air/fuel mixture at precisely the correct time. This provides optimal performance, fuel economy, and control of exhaust emissions. This ignition system uses an ignition coil pack assembly. The ignition coil pack is mounted above the cylinders between the camshafts with short integrated boots connecting the coils to the spark plugs. The driver modules within each ignition coil are commanded ON/OFF by the engine control module (ECM). The ECM primarily uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensors to control sequence, dwell, and timing of the spark. The EI system consists of the following components:

### Crankshaft Position (CKP) Sensor

The CKP sensor works in conjunction with a 58 slotted reluctor wheel attached to the crankshaft. The reluctor wheel consists of 58 slots including a reference gap. Each slot on the reluctor wheel is spaced 6 degrees apart with a 12-degree space for the reference gap. The pulse from the reference gap is known as the sync pulse. The sync pulse is used to synchronize the coil firing sequence with the crankshaft position, while the other slots provide cylinder location during a revolution. As each reluctor wheel slot rotates past the CKP sensor, the resulting change in the magnetic field creates an ON/OFF pulse 58 times per crankshaft revolution. The ECM processes the pulses to determine 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 the CMP sensor inputs. Using the CKP sensor signals in conjunction with the CMP sensor signals, the ECM determines the engine position with great accuracy. The CKP sensor is also used to detect misfire and for tachometer display. The ECM learns the variations between all 58 slots under different speed and load conditions to correctly detect misfires. The CKP sensor circuits consist of a signal circuit, a low reference circuit, and a shielded ground circuit. The CKP sensor signal and low reference circuits are protected from electromagnetic interference by the shielded ground circuit.

### Camshaft Position (CMP) Sensor

The CMP sensors are triggered by a notched reluctor wheels which is part of the intake and the exhaust camshafts. Both of the CMP sensors provide four signal pulses every camshaft revolution. The CMP sensor information is used by the ECM to determine the position of the valve train relative to the crankshaft position. By monitoring the CMP and CKP signals, the ECM can accurately trigger the fuel injectors.

### Ignition Coils

The ignition coil pack directly supplies voltage to each spark plug. Each ignition coil (IC) contains a solid state driver module as its primary element. The ECM will command the IC circuit ON, this allows the current to flow through the primary coil windings for the appropriate time or dwell. When the ECM commands the IC circuit OFF, this will interrupt current flow through the primary coil windings. The magnetic field created by the primary coil windings will collapse across the secondary coil windings, which induces a high voltage. 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. The ignition coil pack is not serviceable and must be replaced as an assembly.

### Engine control module (ECM)

The engine control module (ECM) is responsible for maintaining proper spark and fuel injection timing for all driving conditions. The ignition control (IC) is the method the ECM uses to control spark advance. The primary coil ON/OFF is directly controlled by the ECM. To provide optimum driveability and emissions, the ECM monitors input signals from the following components in calculating ignition spark timing:

• | The crankshaft position (CKP) sensor

• | The engine coolant temperature (ECT) sensor

• | The manifold absolute pressure (MAP) sensor

• | The intake air temperature (IAT) sensor

• | The vehicle speed sensor (VSS)

• | Ambient pressure sensor (BARO)

• | The knock sensor (KS)

• | The vehicle speed sensor (VSS)

• | The mass airflow (MAF) sensor

• | The camshaft position (CMP) sensors