TECHNICAL SERVICE BULLETIN: TRANSMISSION CONTROL UNIT (TCU) GEAR SHIFT LOGIC IMPROVEMENT - This bulletin provides the procedure to improve the gear shift logic of the Transmission Control Unit (TCU) on some 2018MY Optima (JF, JFa) vehicles produced from April 18, 2017 through July 11, 2018, equipped with 2.0L T-GDI and 2.4L GDI engines, which may harsh downshifts (including 2-1 gear change).
