Ignition Systems

IGNITION SYSTEMS

Overview
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 correct vehicle operation and misfire detection.

Integrated Electronic Ignition System

Integrated Electronic Ignition System:

Six Cylinder Integrated Electronic Ignition Waveforms. 4, 8, And 10-Cylinder Are Similar:

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.

The integrated electronic ignition system consists of a crankshaft position (CKP) sensor, coil pack(s), connecting wiring, and PCM. The coil-on-plug (COP) integrated electronic ignition system uses a separate coil per spark plug, and each coil is mounted directly onto the plug. The COP integrated electronic ignition system eliminates the need for spark plug wires, but does require input from the camshaft position (CMP) sensor. Operation of the components are as follows:
1. The CKP sensor is used to indicate the crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted to the crankshaft. The CMP sensor is used by the COP integrated electronic ignition system to identify top dead center of compression of cylinder 1 to synchronize the firing of the individual coils.
2. The PCM uses the CKP signal to calculate a spark target and then fires the coil pack(s) to that target shown. The PCM uses the CMP sensor, not COP integrated electronic ignition systems to identify top dead center of compression of cylinder 1 to synchronize the firing of the individual coils.
3. The coils and coil packs receive their signal from the PCM to fire at a calculated spark target. Each coil within the pack fires 2 spark plugs at the same time. The plugs are paired so that as one fires during the compression stroke the other fires during the exhaust stroke. The next time the coil is fired the situation is reversed. 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 positive voltage (B+) 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 pulse width modulation in the PCM.

4. The PCM processes the CKP signal and uses it to drive the tachometer as the clean tach out (CTO) signal.

Engine Crank/Engine Running
During engine crank the PCM will fire 2 spark plugs simultaneously. Of the 2 plugs simultaneously fired one will be under compression the other will be on the exhaust stroke. Both plugs will fire until camshaft position is identified by a successful camshaft position (CMP) sensor signal. Once camshaft position is identified only the cylinder under compression will be fired.

CMP FMEM
During CMP FMEM the COP ignition works the same as during engine crank. This allows the engine to operate without the PCM knowing if cylinder one is under compression or exhaust.