Ignition Coil: Description and Operation
EI MODULE AND IGNITION COIL HOUSINGEI Module And Ignition Coil Housing:
The EI module, ignition coil housing with coil packs and spark plug boots are bolted as an assembly to the top of the cam cover. The Electronic Ignition (EI) module charges and discharges the coils based on ECM control. The ECM uses a high control signal of near 5 volts to charge up the coil and a low control signal of near 0 volts to discharge the coil. If the coil is charged and the control signal is low, the coil will fire through its secondary towers. The ECM controls spark timing and dwell (spark On-time) under all engine running conditions.
The EI module also has the ability to determine when # 1 and # 3 cylinders have fired on compression by the use of compression sense ignition circuitry. This eliminates the need for a camshaft position sensor. The EI module sends a cam signal out to the ECM whenever it determines cylinders # 1 or # 3 has fired on its compression stroke. Refer to "Electronic Ignition" system description for further details.