Ignition System: Description and Operation

Block Diagram:

DESCRIPTION
The Electronic Ignition System (EI High Data Rate), formerly called EDIS, replaces the distributor to allow more precise control of ignition spark.

Signal Comparison:

OPERATION
The EI system operates by sending crankshaft position information provided by the Variable Resistance Sensor (VRS), also called Crankshaft Position Sensor (CKP), to the Ignition Control Module (ICM). The ICM generates a Profile Ignition Pickup (PIP) signal and sends it to the Powertrain Control Module (PCM). The PCM responds with a Spark Output (SPOUT) signal containing timing advance or retard information. The ICM processes VRS and SPOUT signals to decide which coil in the 6-tower coilpack to fire. The ICM also produces an Ignition Diagnostic Monitor (IDM) signal to indicate a failure and provide a tachometer signal.




4.6L-2V, 4V Car EI (High Data Rate) System and Component Description

System Description

The 4.6L EI (High Data Rate) System consists of a Crankshaft Position (CKP) (variable reluctance) sensor, an Ignition Control Module (ICM), a Powertrain Control Module (PCM), and two four-tower Coil Packs.

The EI (High Data Rate) System operates by sending crankshaft position information from the Crankshaft Position Sensor to the ICM. The ICM generates a PIP signal and sends it to the PCM. The PCM sends a SPOUT signal containing advance or retard timing information back to the ICM. The ICM processes the CKP and SPOUT signals and decides which coils to fire. In addition, the ICM generates an Ignition Diagnostic Monitor (IDM) signal to the PCM which is used to indicate a failure mode and also provide a tach output signal.

Component Description

Crankshaft Position (CKP) Sensor

The CKP sensor is a passive electromagnetic device which senses movement of a 36 minus one-tooth wheel located behind the crankshaft pulley. An AC voltage signal is generated which increases with engine rpm and provides engine speed and crankshaft position information to the ICM.






Component Description

Ignition Control Module (1CM)

The ICM is a microprocessor-based device with coil drivers which make decisions about spark dwell and coil firing. The module turns the coils on and off at the correct time and in the proper sequence based on information from the CKP and a pulse-width modulated signal (SPOUT) generated from the PCM. The ICM receives CKP and SPOUT signals and produces PIP and IDM output signals which are sent to the PCM.






Powertrain Control Module (PCM)

The PCM receives IGN GND and PIP signals from the ICM, then generates a SPOUT signal based upon engine speed, load, temperature and other sensor information. An IDM signal is received from the ICM to determine if an ignition failure mode should be recorded.






Component Description

Coil Pack

The coil is turned on (i.e. coil charging) by the ICM, then turned off, firing two spark plugs at once. One is for the cylinder which is to be fired (on compression stroke), and the other goes to the mating cylinder which is on the exhaust stroke. The next time the coil is fired, the situation is reversed, the next pair of spark plugs will fire according to the engine firing order, etc.