Generally speaking, if we use the VEE, the PIN15 would become the VEE output. So we cannot use PIN15 and PIN16 as input for the backlight. But if we put a backlight jumper on J1, J16 could use PIN16 to control the backlight. For details, please refer to the below drawing.

Fig 1: Backlight Jump

Fig 2: Vee use Pin15 as output , backlight use the Pin16 to control