Ignition Control Module -Cranking

The picture above describes IC operation during cranking. To help understand how the circuit operates, a relay with a double set of of contacts is shown inside the IC module. Actually solid state circuitry is used, but for illustration purposes a relay makes it easier to visualize and explain.

Module Mode (cranking mode)

During cranking, the relay is de-energized, allowing a set of contacts to connect the pick-up coil to the base of the transistor. When the pick-up coil applies a positive voltage the transistor turns “on”, when voltage is removed the transistor turns “off”. When it is off the primary current stops and a spark is developed. Cranking is defined as RPM below 400, at this time the ECM has grounded the IC line at terminal “E”and has no voltage applied to the by-pass line at terminal “B”. At this point the IC module has ignition control. A small amount of advance is built into the IC module, in case the engine remains or defaults to module mode.