ELECTRONIC SPARK ADVANCE (ESA) The ECU is programmed with data for optimum ignition timing under any and all operating conditions. Using data provided by sensors which monitor various engine functions (rpm, intake air volume, eng. temperature, etc.) the microcomputer (ECU) triggers the spark at precisely the right instant. ESA SYSTEM CIRCUIT +B Ignition Coil w/Igniter ECU Spark Plugs To Tachometer Service Connector IGt Igniter Assy IGt Distributor G Ne G-G E1 IG0263