For 1990-2009 cars

### Electronic Ignition (EI) System Operation

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) collects information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensors to determine the sequence, dwell, and timing of the spark for each cylinder. The ECM transmits a frequency signal to the ignition control (IC) module assembly on the appropriate IC circuit to fire the spark plugs.

### Crankshaft Position (CKP) Sensor

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 externally magnetic biased digital output integrated circuit sensing device. The sensor provides a pulse for each magnetic pole of the magnetic encoder wheel on the crankshaft. Each pole on the encoder wheel is spaced at 60-pole spacing, with 2 missing poles 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 encoder wheel, to the ECM as each pole on the wheel rotates past the CKP sensor. The ECM uses each CKP signal pulse to determine crankshaft speed and decodes the crankshaft encoder 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.

### Crankshaft Encoder Wheel

The crankshaft encoder wheel is part of the crankshaft. The encoder wheel consists of 58 poles and a reference gap. Each pole on the encoder 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 poles provide cylinder location during a revolution.

### Camshaft Position (CMP) Sensor

The camshaft position (CMP) sensor is triggered by a notched reluctor wheel built onto the intake camshaft sprocket. The CMP sensor provides four signal pulses every camshaft revolution. Each notch, or feature of the reluctor wheel is of a different size which is used to identify the compression stroke of each cylinder and to enable sequential fuel injection. The CMP sensor is connected to the ECM by the following circuits:

• | 5-volt reference

• | Low reference

• | Signal

### Ignition Coil/Module Assembly

The ignition coil/module assembly used on this engine integrates the 4 coils and the module within a single sealed component.

The ignition coil/module has the following circuits:

• | Ignition voltage

• | Ground

• | 4 ignition control (IC)

The ECM controls the individual coils by transmitting timing pulses on the IC circuit of each ignition coil to enable a spark event.

The spark plugs are connected to each coil by a short boot. The boot contains a spring that conducts the spark energy from the coil to the spark plug. The spark plug electrode is tipped with platinum for long wear and higher efficiency.

### Engine Control Module (ECM)

The ECM controls all ignition system functions, and constantly adjusts the spark timing. The ECM monitors information from various sensor inputs that include the following:

• | Throttle position (TP) sensor

• | Engine coolant temperature (ECT) sensor

• | Mass air flow (MAF) sensor

• | Intake air temperature (IAT) sensor

• | Vehicle speed sensor (VSS)

• | Engine knock sensor (KS)

• | Barometric (BARO) pressure sensor