Fast charge not working

a customer brought in a phone complaining of slow charging. its charging just fine at 1a, but i cant get the 2a fast charging working. i made sure the fast charge option was turned on in the settings and that the port was clear of any debris and it is. I also tested my cables on another device with usb amp meter and that device is charging at 2a just fine so i know its not the cable. also transplanted the logic board into another s6 housing with a charge port and battery i know are good, and its still only charging at 1a. so i guess its a logic board issue? has anyone seen this before? or replaced the ic responsible for fast charging?