Electronic Spark Control & Electronic Module Retard Ignition System: Description

The Electronic Spark Control (ESC) system and the Electronic Module Retard (EMR) system perform the same function, retarding ignition timing. The difference between the two systems is when the timing is retarded. The ESC system, which is used on engines equipped with the C4 emission system, retards timing whenever engine detonation is detected by a detonation sensor. The ESC system retards ignition timing a variable amount. The amount is a function of engine detonation. The EMR system retards ignition timing a fixed amount when the engine coolant temperature is within a predetermined specification.