General Description

PURPOSE
The Ignition System is designed to ignite the compressed air/fuel mixture in an internal combustion engine by a high voltage spark from an ignition coil. The ignition system also provides engine timing information to the Powertrain Control Module (PCM) for proper vehicle operation and misfire detection.

COMPONENTS
The Integrated Electronic Ignition (EI) system consists of a Crankshaft Position (CKP) sensor, Coil On Plug (COP) units, connecting wiring, and PCM. The COP Integrated EI System uses a separate coil per spark plug and each coil is mounted directly onto the plug. This eliminates the need for spark plug wires but does require input from the Camshaft Position (CMP) sensor.

OPERATION
- The CKP Sensor is used to indicate crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted to the crankshaft.

- The CMP Sensor is used to identify top dead center of compression of cylinder 1 to synchronize the firing of the individual coils.

- The PCM uses the CMP Sensor on COP Integrated EI Systems to identify top dead center of compression of cylinder 1 to synchronize the firing of the individual coils.

- The coils receive their signal from the PCM to fire at a calculated spark target. The COP system fires only one spark plug per coil and only on the compression stroke.

- The PCM acts as an electronic switch to ground in the coil primary circuit. When the switch is closed, battery power applied to the coil primary circuit builds a magnetic field around the primary coil. When the switch opens, the power is interrupted and the primary field collapses inducing the high voltage in the secondary coil windings and the spark plug is fired. A kickback voltage spike occurs when the primary field collapses. The PCM uses this voltage spike to generate an Ignition Diagnostic Monitor (IDM) signal. IDM communicates information by pulsewidth modulation in the PCM.

- The PCM processes the CKP signal and uses it to drive the tachometer as the Clean Tach Out (CTO) signal.

NOTE: Electronic Ignition engine timing is entirely controlled by the PCM. Electronic Ignition engine timing is NOT adjustable. Do not attempt to check base timing. You will receive false readings.