Where is the ignition failure sensor on a 2004 Kia Optima LX 4 cylinder?

The 2004 Kia Optima LX 4-cylinder engine does not have an ignition failure sensor. The car's ignition system is controlled by the engine control unit (ECU), which monitors various sensors and adjusts the ignition timing accordingly. If there is a problem with the ignition system, the ECU will typically store a diagnostic trouble code (DTC). You can retrieve these codes using a scan tool and then use them to diagnose the problem.