TECHNICAL SERVICE BULLETIN: PRODUCT IMPROVEMENT (PI1805Y/Z) - This bulletin provides information related to the Technical Service Bulletin previously published in (PI1805) titled "Knock Sensor Detection System - ECU Logic Improvement" for certain 2019MY Optima (JFa), Sorento (UMa) and Sportage (QL) vehicles equipped with a 2.4L GDI or 2.0L T-GDI engine. Specifically, this bulletin provides instructions on which procedures to follow if, after installation of the KSDS, any one of the subject vehicles below return to the dealer with Diagnostic Trouble Code (DTC) P1326 (Knock Signal Range/Performance).