how do i turn off o/d function?

"O/D function" is turning on and off the overdrive gear of the automatic transmission. Are you seeing the O/D indicator blink? If you are seeing the indicator blink, it indicates an electronic transmission fault has been sensed and is being communicated to the driver. This means testing must be performed. Electronic transmission diagnostic testing will determine what is happening that is likely causing your engagement issue that you are experiencing. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops